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Author Report for: Qi Q

Title: Computational design of a cutinase for plastic biodegradation by mining molecular dynamics simulations trajectories
Li Q, Zheng Y, Su T, Wang Q, Liang Q, Zhang Z, Qi Q, Tian J
Ref: Comput Struct Biotechnol J, 20:459, 2022 : PubMed
Abstract


ESTHER: Li_2022_Comput.Struct.Biotechnol.J_20_459
PubMedSearch: Li 2022 Comput.Struct.Biotechnol.J 20 459
PubMedID: 35070168
Gene_locus related to this paper: thefu-q6a0i3

Abstract

Polyethylene terephthalate (PET) has caused serious environmental concerns but could be degraded at high temperature. Previous studies show that cutinase from Thermobifida fusca KW3 (TfCut2) is capable of degrading and upcycling PET but is limited by its thermal stability. Nowadays, Popular protein stability modification methods rely mostly on the crystal structures, but ignore the fact that the actual conformation of protein is complex and constantly changing. To solve these problems, we developed a computational approach to design variants with enhanced protein thermal stability by mining Molecular Dynamics simulation trajectories using Machine Learning methods (MDL). The optimal classification accuracy and the optimal Pearson correlation coefficient of MDL model were 0.780 and 0.716, respectively. And we successfully designed variants with high deltaT (m) values using MDL method. The optimal variant S121P/D174S/D204P had the highest deltaT (m) value of 9.3 degreesC, and the PET degradation ratio increased by 46.42-fold at 70 degC, compared with that of wild type TfCut2. These results deepen our understanding on the complex conformations of proteins and may enhance the plastic recycling and sustainability at glass transition temperature.



        

Title: Preparation and Characterization of Magnetic Metal-Organic Frameworks Functionalized by Ionic Liquid as Supports for Immobilization of Pancreatic Lipase
Li X, Jia Y, Li J, Zhang P, Li T, Lu L, Yao H, Liu J, Zhu Z and Xu L <24 more author(s)> Li X, Jia Y, Li J, Zhang P, Li T, Lu L, Yao H, Liu J, Zhu Z, Xu J, Morita S, Yamada H, Koga K, Ota W, Furuta T, Yamatsu A, Kim M, Li C, Tang W, Chen S, He J, Zhu X, Li H, Peng Y, Li M, Dai X, Li A, Qi Q, Wang W, Cao J, Jiang Z, Liu R, Suo H, Xu L (- 24)
Ref: Molecules, 27:, 2022 : PubMed
Abstract


ESTHER: Li_2022_Molecules_27_
PubMedSearch: Li 2022 Molecules 27
PubMedID: 35630563 35956860 36234873 36296392

Abstract

Enzymes are difficult to recycle, which limits their large-scale industrial applications. In this work, an ionic liquid-modified magnetic metal-organic framework composite, IL-Fe(3)O(4)@UiO-66-NH(2), was prepared and used as a support for enzyme immobilization. The properties of the support were characterized with X-ray powder diffraction (XRD), Fourier-transform infrared (FTIR) spectra, transmission electron microscopy (TEM), scanning electronic microscopy (SEM), and so on. The catalytic performance of the immobilized enzyme was also investigated in the hydrolysis reaction of glyceryl triacetate. Compared with soluble porcine pancreatic lipase (PPL), immobilized lipase (PPL-IL-Fe(3)O(4)@UiO-66-NH(2)) had greater catalytic activity under reaction conditions. It also showed better thermal stability and anti-denaturant properties. The specific activity of PPL-IL-Fe(3)O(4)@UiO-66-NH(2) was 2.3 times higher than that of soluble PPL. After 10 repeated catalytic cycles, the residual activity of PPL-IL-Fe(3)O(4)@UiO-66-NH(2) reached 74.4%, which was higher than that of PPL-Fe(3)O(4)@UiO-66-NH(2) (62.3%). In addition, kinetic parameter tests revealed that PPL-IL-Fe(3)O(4)@UiO-66-NH(2) had a stronger affinity to the substrate and, thus, exhibited higher catalytic efficiency. The results demonstrated that Fe(3)O(4)@UiO-66-NH(2) modified by ionic liquids has great potential for immobilized enzymes.



        

Title: Molecular Mechanisms Underlying Metabolic Resistance to Cyflumetofen and Bifenthrin in Tetranychus urticae Koch on Cowpea
Liu TT, Liu XT, Huang GL, Liu L, Chen QX, Wang Q, Liu P, Zheng Y, Yuan Y and Huang J <17 more author(s)> Liu TT, Liu XT, Huang GL, Liu L, Chen QX, Wang Q, Liu P, Zheng Y, Yuan Y, Zhang T, Li Q, Liang Q, Su T, Qi Q, Liu G, Meng X, Ren Y, Zhang M, Chen Z, Zhang Z, Pang X, Zhang X, Liu Z, Wu F, Liang W, Zhou L, Huang J (- 17)
Ref: Int J Mol Sci, 23:, 2022 : PubMed
Abstract


ESTHER: Liu_2022_Int.J.Mol.Sci_23_
PubMedSearch: Liu 2022 Int.J.Mol.Sci 23
PubMedID: 35269668 36232310 36233017 36555861
Inhibitor(s) related to this paper: Caffeine

Abstract

Tetranychus urticae Koch (T. urticae) is one of the most tremendous herbivores due to its polyphagous characteristics, and is resistant to most acaricides. In this study, enzyme-linked immunosorbent assay (ELISA), transcriptome sequencing (RNA-seq) and quantitative real-time PCR (qRT-PCR) were carried out to analyze the mechanisms of T. urticae metabolic resistance to cyflumetofen and bifenthrin on cowpea. The enzyme activity of UDP-glucuronosyltransferases (UGTs) and carboxylesterases (CarEs) in the cyflumetofen-resistant (R_cfm) strain significantly decreased, while that of cytochrome P450 monooxygenases (P450s) significantly increased. Meanwhile, the activities of glutathione-S-transferases (GSTs), CarEs and P450s in the bifenthrin-resistant (R_bft) strain were significantly higher than those in the susceptible strain (Lab_SS). According to the Kyoto Encyclopedia of Genes and Genomes (KEGG) and Gene Ontology (GO) analyses, in the R_cfm mite strain, two carboxyl/cholinesterase (CCE) genes and two P450 genes were upregulated and one gene was downregulated, namely CYP392E7; in the R_bft mite strain, eleven CCE, nine UGT, two P450, four GST and three ABC genes were upregulated, while four CCE and three P450 genes were downregulated. Additionally, 94 differentially expressed genes (DEGs) were common to the two resistant groups. Specifically, TuCCE46 and TuCCE70 were upregulated in both resistant groups. Furthermore, the qRT-PCR validation data were consistent with those from the transcriptome sequencing analysis. Specifically, TuCCE46 (3.37-fold) was significantly upregulated in the R_cfm strain, while in the R_bft strain, TeturUGT22 (5.29-fold), teturUGT58p (1.74-fold), CYP392A11 (2.89-fold) and TuGSTd15 (5.12-fold) were significantly upregulated and TuCCE01 (0.13-fold) and CYP392A2p (0.07-fold) were significantly downregulated. Our study indicates that TuCCE46 might play the most important role in resistance to cyflumetofen, and TuCCE01, teturUGT58p, teturUGT22, CYP392A11, TuGSTd15, TuGSTm09 and TuABCG-13 were prominent in the resistance to bifenthrin. These findings provide further insight into the critical genes involved in the metabolic resistance of T. urticae to cyflumetofen and bifenthrin.



        

Title: Ndrg3 gene regulates DSB repair during meiosis through modulation the ERK signal pathway in the male germ cells
Pan H, Zhang X, Jiang H, Jiang X, Wang L, Qi Q, Bi Y, Wang J, Shi Q, Li R
Ref: Sci Rep, 7:44440, 2017 : PubMed
Abstract


ESTHER: Pan_2017_Sci.Rep_7_44440
PubMedSearch: Pan 2017 Sci.Rep 7 44440
PubMedID: 28290521

Abstract

The N-myc downstream regulated gene (NDRG) family consists of 4 members, NDRG-1, -2, -3, -4. Physiologically, we found Ndrg3, a critical gene which led to homologous lethality in the early embryo development, regulated the male meiosis in mouse. The expression of Ndrg3 was enhanced specifically in germ cells, and reached its peak level in the pachytene stage spermatocyte. Haplo-insufficiency of Ndrg3 gene led to sub-infertility during the male early maturation. In the Ndrg3(+/-) germ cells, some meiosis events such as DSB repair and synaptonemal complex formation were impaired. Disturbances on meiotic prophase progression and spermatogenesis were observed. In mechanism, the attenuation of pERK1/2 signaling was detected in the heterozygous testis. With our primary spermatocyte culture system, we found that lactate promoted DSB repair via ERK1/2 signaling in the male mouse germ cells in vitro. Deficiency of Ndrg3 gene attenuated the activation of ERK which further led to the aberrancy of DSB repair in the male germ cells in mouse. Taken together, we reported that Ndrg3 gene modulated the lactate induced ERK pathway to facilitate DSB repair in male germ cells, which further regulated meiosis and subsequently fertility in male mouse.



        

Title: The structure of a complex of the lactonohydrolase zearalenone hydrolase with the hydrolysis product of zearalenone at 1.60 A resolution
Qi Q, Yang WJ, Zhou HJ, Ming DM, Sun KL, Xu TY, Hu XJ, Lv H
Ref: Acta Crystallographica F Struct Biol Commun, 73:376, 2017 : PubMed
Abstract


ESTHER: Qi_2017_Acta.Crystallogr.F.Struct.Biol.Commun_73_376
PubMedSearch: Qi 2017 Acta.Crystallogr.F.Struct.Biol.Commun 73 376
PubMedID: 28695844
Gene_locus related to this paper: biooc-ZHD101
Inhibitor(s) related to this paper: ZFR

Abstract

Zearalenone hydrolase (ZHD) is an alpha/beta-hydrolase that detoxifies and degrades the lactone zearalenone (ZEN), a naturally occurring oestrogenic mycotoxin that contaminates crops. Several apoenzyme and enzyme-substrate complex structures have been reported in the resolution range 2.4-2.6 A. However, the properties and mechanism of this enzyme are not yet fully understood. Here, a 1.60 A resolution structure of a ZHD-product complex is reported which was determined from a C-terminally His6-tagged ZHD crystal soaked with 2 mM ZEN for 30 min. It shows that after the lactone-bond cleavage, the phenol-ring region moves closer to residues Leu132, Tyr187 and Pro188, while the lactone-ring region barely moves. Comparisons of the ZHD-substrate and ZHD-product structures show that the hydrophilic interactions change, especially Trp183 N1, which shifts from contacting O2 to O12', suggesting that Trp183 is responsible for the unidirectional translational movement of the phenol ring. This structure provides information on the final stage of the catalytic mechanism of zearalenone hydrolysis.



        

Title: Gambogic acid potentiates clopidogrel-induced apoptosis and attenuates irinotecan-induced apoptosis through down-regulating human carboxylesterase 1 and -2
Ning R, Wang XP, Zhan YR, Qi Q, Huang XF, Hu G, Guo QL, Liu W, Yang J
Ref: Xenobiotica, :1, 2016 : PubMed
Abstract


ESTHER: Ning_2016_Xenobiotica__1
PubMedSearch: Ning 2016 Xenobiotica 1
PubMedID: 26750665

Abstract

1. In this study, we report that gambogic acid (GA), a promising anticancer agent, potentiates clopidogrel-induced apoptosis and attenuates CPT-11-induced apoptosis by down-regulating human carboxylesterase (CES) 1 and -2 via ERK and p38 MAPK pathway activation, which provides a molecular explanation linking the effect of drug combination directly to the decreased capacity of hydrolytic biotransformation. 2. The expression levels of CES1 and CES2 decreased significantly in a concentration- and time-dependent manner in response to GA in Huh7 and HepG2 cells; hydrolytic activity was also reduced. 3. The results showed that pretreatment with GA potentiated clopidogrel-induced apoptosis by down-regulating CES1. Moreover, the GA-mediated repression of CES2 attenuated CPT-11-induced apoptosis. 4. Furthermore, the ERK and p38 MAPK pathways were involved in the GA-mediated down-regulation of CES1 and CES2. 5. Taken together, our data suggest that GA is a potent repressor of CES1 and CES2 and that combination with GA will affect the metabolism of drugs containing ester bonds.



        

Title: The Genomes of Oryza sativa: a history of duplications
Yu J, Wang J, Lin W, Li S, Li H, Zhou J, Ni P, Dong W, Hu S and Yang H <88 more author(s)> Yu J, Wang J, Lin W, Li S, Li H, Zhou J, Ni P, Dong W, Hu S, Zeng C, Zhang J, Zhang Y, Li R, Xu Z, Li X, Zheng H, Cong L, Lin L, Yin J, Geng J, Li G, Shi J, Liu J, Lv H, Li J, Deng Y, Ran L, Shi X, Wang X, Wu Q, Li C, Ren X, Li D, Liu D, Zhang X, Ji Z, Zhao W, Sun Y, Zhang Z, Bao J, Han Y, Dong L, Ji J, Chen P, Wu S, Xiao Y, Bu D, Tan J, Yang L, Ye C, Xu J, Zhou Y, Yu Y, Zhang B, Zhuang S, Wei H, Liu B, Lei M, Yu H, Li Y, Xu H, Wei S, He X, Fang L, Huang X, Su Z, Tong W, Tong Z, Ye J, Wang L, Lei T, Chen C, Chen H, Huang H, Zhang F, Li N, Zhao C, Huang Y, Li L, Xi Y, Qi Q, Li W, Hu W, Tian X, Jiao Y, Liang X, Jin J, Gao L, Zheng W, Hao B, Liu S, Wang W, Yuan L, Cao M, McDermott J, Samudrala R, Wong GK, Yang H (- 88)
Ref: PLoS Biol, 3:e38, 2005 : PubMed
Abstract


ESTHER: Yu_2005_PLoS.Biol_3_e38
PubMedSearch: Yu 2005 PLoS.Biol 3 e38
PubMedID: 15685292
Gene_locus related to this paper: orysa-Q7XTC5, orysa-Q852M6, orysa-Q8GSE8, orysa-Q9S7P1, orysa-Q9FYP7, orysa-Q5ZBH3, orysa-Q5ZA26, orysa-Q5JLP6, orysa-Q8H5P9, orysa-Q8H5P5, orysa-Q7F1Y5, orysa-Q949C9, orysa-cbp1, orysa-cbp3, orysa-cbpx, orysa-Q33B71, orysa-Q8GSJ3, orysa-LPL1, orysa-Q6YSZ8, orysa-Q8S5X5, orysa-Q8LIG3, orysa-Q6K7F5, orysa-Q7F1B1, orysa-Q8H4S9, orysa-Q69UB1, orysa-Q9FW17, orysa-Q337C3, orysa-Q7F959, orysa-Q84QZ6, orysa-Q84QY7, orysa-Q851E3, orysa-Q6YTH5, orysa-Q0JK71, orysa-Q8S1D9, orysa-Q5N8V4, orysa-Q0JCY4, orysa-Q8GTK2, orysa-B9EWJ8, orysa-Q8H3K6, orysa-Q6ZDG8, orysa-Q6ZDG6, orysa-Q6ZDG5, orysa-Q6ZDG4, orysa-Q5NAI4, orysa-Q658B2, orysa-Q5JMQ8, orysa-Q5QMD9, orysa-Q5N7L1, orysa-Q8RYV9, orysa-Q8H3R3, orysa-Q5SNH3, orysa-Q8W0F0, orysa-pir7a, orysa-pir7b, orysa-q2qlm4, orysa-q2qm78, orysa-q2qm82, orysa-q2qn31, orysa-q2qnj4, orysa-q2qnt9, orysa-q2qur1, orysa-q2qx94, orysa-q2qyi1, orysa-q2qyj1, orysa-q2r051, orysa-q2r077, orysa-q2ram0, orysa-q2rat1, orysa-q2rbb3, orysa-Q4VWY7, orysa-q5na00, orysa-q5nbu1, orysa-Q5QLC0, orysa-q5smv5, orysa-Q5VP27, orysa-q5vrt2, orysa-q5w6c5, orysa-q5z5a3, orysa-q5z9i2, orysa-q5z417, orysa-q5z901, orysa-Q5ZAM8, orysa-Q5ZBI5, orysa-Q5ZCR3, orysa-q6atz0, orysa-q6ave2, orysa-q6f358, orysa-q6h6s1, orysa-q6h7i6, orysa-q6i5q3, orysa-q6i5u7, orysa-q6j657, orysa-q6k3d9, orysa-q6k4q2, orysa-q6k880, orysa-q6l5b6, orysa-Q6L5F5, orysa-q6l556, orysj-q6yse8, orysa-q6yy42, orysa-q6yzk1, orysa-q6z8b1, orysa-q6z995, orysa-q6zc62, orysa-q6zia4, orysa-q6zjq6, orysa-q7x7y5, orysa-Q7XC50, orysa-q7xej4, orysa-q7xem8, orysa-q7xkj9, orysa-q7xr62, orysa-q7xr63, orysa-q7xr64, orysa-q7xsg1, orysa-q7xsq2, orysa-q7xts6, orysa-q7xv53, orysa-Q7XVB5, orysa-Q8L562, orysa-Q8LQS5, orysa-Q8RZ40, orysa-Q8RZ79, orysa-Q8S0U8, orysa-Q8S0V0, orysa-Q8S125, orysa-Q8SAY7, orysa-Q8SAY9, orysa-Q8W3C6, orysa-Q8W3F2, orysa-Q8W3F4, orysa-Q8W3F6, orysa-Q9LHX5, orysa-q33aq0, orysa-q53lh1, orysa-q53m20, orysa-q53nd8, orysa-q60e79, orysa-q60ew8, orysa-q67iz2, orysa-q67iz3, orysa-q67iz7, orysa-q67iz8, orysa-q67j02, orysa-q67j05, orysa-q67j07, orysa-q67j09, orysa-q67j10, orysa-q67tr6, orysa-q67tv0, orysa-q67uz1, orysa-q67v34, orysa-q67wz5, orysa-q69j38, orysa-q69k08, orysa-q69md7, orysa-q69me0, orysa-q69pf3, orysa-q69ti3, orysa-q69xr2, orysa-q69y12, orysa-q69y21, orysa-q75hy2, orysa-q75i01, orysa-Q94JD7, orysa-Q0J0A4, orysa-q651a8, orysa-q651z3, orysa-q652g4, orysa-q688m0, orysa-q688m8, orysa-q688m9, orysa-Q6H8G1, orysi-a2wn01, orysi-a2xc83, orysi-a2yh83, orysi-a2z179, orysi-a2zef2, orysi-b8a7e6, orysi-b8a7e7, orysi-b8bfe5, orysi-b8bhp9, orysj-a3b9l8, orysj-b9eub8, orysj-b9eya5, orysj-b9fi05, orysj-b9fkb0, orysj-b9fn42, orysj-b9gbb7, orysj-cgep, orysj-PLA7, orysj-q0d4u5, orysj-q0djj0, orysj-q0jaf0, orysj-q5jl22, orysj-q5jlw7, orysj-q5z419, orysj-q6h7q9, orysj-q6yvk6, orysj-q6z6i1, orysj-q7f8x1, orysj-q7xcx3, orysj-q9fwm6, orysj-q10j20, orysj-q10ss2, orysj-q69uw6, orysj-q94d71, orysj-q338c0, orysi-b8bly4, orysj-b9gbs4, orysi-a2zb88, orysj-b9gbs1, orysi-b8b698, orysj-pla4, orysj-pla1

Abstract

We report improved whole-genome shotgun sequences for the genomes of indica and japonica rice, both with multimegabase contiguity, or almost 1,000-fold improvement over the drafts of 2002. Tested against a nonredundant collection of 19,079 full-length cDNAs, 97.7% of the genes are aligned, without fragmentation, to the mapped super-scaffolds of one or the other genome. We introduce a gene identification procedure for plants that does not rely on similarity to known genes to remove erroneous predictions resulting from transposable elements. Using the available EST data to adjust for residual errors in the predictions, the estimated gene count is at least 38,000-40,000. Only 2%-3% of the genes are unique to any one subspecies, comparable to the amount of sequence that might still be missing. Despite this lack of variation in gene content, there is enormous variation in the intergenic regions. At least a quarter of the two sequences could not be aligned, and where they could be aligned, single nucleotide polymorphism (SNP) rates varied from as little as 3.0 SNP/kb in the coding regions to 27.6 SNP/kb in the transposable elements. A more inclusive new approach for analyzing duplication history is introduced here. It reveals an ancient whole-genome duplication, a recent segmental duplication on Chromosomes 11 and 12, and massive ongoing individual gene duplications. We find 18 distinct pairs of duplicated segments that cover 65.7% of the genome; 17 of these pairs date back to a common time before the divergence of the grasses. More important, ongoing individual gene duplications provide a never-ending source of raw material for gene genesis and are major contributors to the differences between members of the grass family.



        

Title: Biochemical characterization of the Pseudomonas putida 3-hydroxyacyl ACP:CoA transacylase, which diverts intermediates of fatty acid de novo biosynthesis
Hoffmann N, Amara AA, Beermann BB, Qi Q, Hinz HJ, Rehm BH
Ref: Journal of Biological Chemistry, 277:42926, 2002 : PubMed
Abstract


ESTHER: Hoffmann_2002_J.Biol.Chem_277_42926
PubMedSearch: Hoffmann 2002 J.Biol.Chem 277 42926
PubMedID: 12200450

Abstract

The 3-hydroxyacyl ACP:CoA transacylase (PhaG) was recently identified in various Pseudomonas species and catalyzes the diversion of ACP thioester intermediates of fatty acid de novo biosynthesis toward the respective CoA thioesters, which serve as precursors for polyester and rhamnolipid biosynthesis. PhaG from Pseudomonas putida was overproduced in Escherichia coli as a C-terminal hexahistidine-tagged (His(6)) fusion protein in high yield. The His(6)-PhaG was purified to homogeneity by refolding of PhaG obtained from inclusion bodies, and a new enzyme assay was established. Kinetic analysis of the 3-hydroxyacyl transfer to ACP, catalyzed by His(6)-PhaG, gave K(0.5) values of 28 microm (ACP) and 65 microm (3-hydroxyacyl-CoA) considering V(max) values of 11.7 milliunits/mg and 12.4 milliunits/mg, respectively. A Hill coefficient of 1.38 (ACP) and 1.32 (3-hydroxyacyl-CoA) indicated a positive substrate cooperativity. Subcellular localization studies showed that PhaG is not attached to polyester granules and resides in the cytosol. Gel filtration chromatography analysis in combination with light scattering analysis indicated substrate-induced dimerization of the transacylase. A threading model of PhaG was developed based on the homology to an epoxide hydrolase (1cqz). In addition, the alignment with the alpha/beta-hydrolase fold region indicated that PhaG belongs to alpha/beta-hydrolase superfamily. Accordingly, CD analysis suggested a secondary structure composition of 29% alpha-helix, 22% beta-sheet, 18% beta-turn, and 31% random coil. Site-specific mutagenesis of seven highly conserved amino acid residues (Asp-60, Ser-102, His-177, Asp-182, His-192, Asp-223, His-251) was used to validate the protein model and to investigate organization of the transacylase active site. Only the D182(A/E) mutation was permissive with about 30% specific activity of the wild type enzyme. Furthermore, this mutation caused a change in substrate specificity, indicating a functional role in substrate binding. The serine-specific agent phenylmethylsulfonyl fluoride (PMSF) or the histidine-specific agent diethylpyrocarbonate (DEPC) caused inhibition of 3-hydroxyacyl transfer to holo-ACP, and the S102(A/T) or H251(A/R) PhaG mutant was incapable of catalyzing 3-hydroxyacyl transfer, suggesting that these residues are part of a catalytic triad.



        

Title: Polyhydroxybutyrate biosynthesis in Caulobacter crescentus: molecular characterization of the polyhydroxybutyrate synthase
Qi Q, Rehm BH
Ref: Microbiology, 147:3353, 2001 : PubMed
Abstract


ESTHER: Qi_2001_Microbiology_147_3353
PubMedSearch: Qi 2001 Microbiology 147 3353
PubMedID: 11739767
Gene_locus related to this paper: caucr-PHAZ

Abstract

Caulobacter crescentus was investigated with respect to polyhydroxybutyrate (PHB) biosynthesis. Polyhydroxyalkanoate (PHA) accumulation contributing to approximately 18% of the cell dry weight was obtained in the presence of glucose. Gas chromatography-mass spectrometry and gel permeation chromatography of the purified PHA showed that this polyester was solely composed of 3-hydroxybutyrate and had a weight average molar mass of 5.5 x 10(5) g mol(-1) and a polydispersity of 1.6. An ORF encoding a conserved, hypothetical protein which shared approximately 47% identity with the PHB synthase from Azorhizobium caulinodans was identified within the complete C. crescentus genomic sequence. This putative C. crescentus PHB synthase gene, phaC, consisted of a 2019 nt stretch of DNA (encoding 673 aa residues), which encoded a PHB synthase with a molecular mass of approximately 73 kDa. This is currently the largest PHA synthase identified. The phaC coding region was subcloned into vector pBBR1-JO2 under lac promoter control. The resulting plasmid, pQQ4, mediated PHB accumulation in the mutant Ralstonia eutropha PHB(-)4 and recombinant Escherichia coli JM109(pBHR69), which produced the beta-ketothiolase and acetoacetyl-CoA reductase from R. eutropha, contributing to approximately 62% and 6% of cell dry weight, respectively. Functional expression of the coding region of phaC was confirmed by immunoblotting and in vitro PHB synthase activity.