(Below N is a link to NCBI taxonomic web page and E link to ESTHER at designed phylum.) > cellular organisms: NE > Archaea: NE > Euryarchaeota: NE > Thermococci: NE > Thermococcales: NE > Thermococcaceae: NE > Pyrococcus: NE > Pyrococcus horikoshii: NE
LegendThis sequence has been compared to family alignement (MSA) red => minority aminoacid blue => majority aminoacid color intensity => conservation rate title => sequence position(MSA position)aminoacid rate Catalytic site Catalytic site in the MSA MTSIEWDEKTFTKFAYLSDPRTRKNLVAYVLTKANLESNKYENTIVIENL EDGSRKFIEDASMPRISPDGKKIAFMRFNEEKKTAQIWVADLKTLSAKKV LEAKNIRSIEWNQDSRRLLAVGFKRREDEDFIFEDDVPAWFDNMGFFDGE KTTFWVIDTEGEEVIEQFEKPRFSSGIWHGDSIVVSVPHRDVIPRYFKYW DIYLWKDGEEEKLFEKVSFYAIDSDGERILLYGKPEKKYVSEHDKIYIYD GEVKGILDDIDREVAQAKIRNGKVYFTLFEEGSVNLYLWDGEVREIAKGK HWIMGFDADERLIYLKETATRPAELYLWDGEERQLTDYNGLIFKKLKTFE PRHFRFKSIDLELDGWYIKPEIKEGEKAPVIVFVHGGPKGMYGYYFKYEM QLMASKGYYIVYVNPRGSNGYSEDFALRVLERTGLEDFQDILNGIEEFLR LEPQADRERIGITGISYGGYMTNWALTQSDLFKAGISENGISYWLTSYAF SDIGLWFDKEVIGDNPLENENYRKLSPLFYAKNVKAPLLLIHSLEDYRCP LDQSLMFYHVLKDLGKEVYIAIFKKGAHGHSIRGSPRHRMKRYKLFMEFF ERKLKKYEEGFDVEKILKEEKK
Oligopeptidases impose a size limitation on their substrates, the mechanism of which has long been under debate. Here we present the structure of a hexameric serine protease, an oligopeptidase from Pyrococcus horikoshii (PhAAP), revealing a complex, self-compartmentalized inner space, where substrates may access the monomer active sites passing through a double-gated "check-in" system, first passing through a pore on the hexamer surface and then turning to enter through an even smaller opening at the monomers' domain interface. This substrate screening strategy is unique within the family. We found that among oligopeptidases, a residue of the catalytic apparatus is positioned near an amylogenic beta-edge, which needs to be protected to prevent aggregation, and we found that different oligopeptidases use different strategies to achieve such an end. We propose that self-assembly within the family results in characteristically different substrate selection mechanisms coupled to different multimerization states.
We have overexpressed in E. coli, purified and investigated the kinetic, thermodynamic and biophysical properties of an acylaminoacyl peptidase (AAP), from the thermophile Pyrococcus horikoshii (PhAAP). It was shown that the electrostatic environment of the catalytic site of PhAAP substantially influenced the pH dependence of the specificity rate constant (k(cat)/K(m)). However, 0.3 M NaCl, which depressed the electrostatic effects, simplified the complex pH-rate profile. The rate of formation of the enzyme-substrate complex (k(1)) was obtained from a non-linear Arrhenius plot. The lack of substrate leaving group effects indicated that k(1) is the rate determining step in the catalysis. DSC and CD measurements demonstrated that PhAAP displayed a stable structure in the catalytically competent pH range. It was shown that PhAAP is not just an acylaminoacyl peptidase, but it also has an endopeptidase activity and so differs from the mammalian AAPs. Size exclusion chromatography with PhAAP revealed a hexameric structure, which is unique among the known members of the prolyl oligopeptidase family that includes AAPs and suggests that its cellular function may be different from that of the dimeric AAP also found in the same organism.
The complete sequence of the genome of a hyper-thermophilic archaebacterium, Pyrococcus horikoshii OT3, has been determined by assembling the sequences of the physical map-based contigs of fosmid clones and of long polymerase chain reaction (PCR) products which were used for gap-filling. The entire length of the genome was 1,738,505 bp. The authenticity of the entire genome sequence was supported by restriction analysis of long PCR products, which were directly amplified from the genomic DNA. As the potential protein-coding regions, a total of 2061 open reading frames (ORFs) were assigned, and by similarity search against public databases, 406 (19.7%) were related to genes with putative function and 453 (22.0%) to the sequences registered but with unknown function. The remaining 1202 ORFs (58.3%) did not show any significant similarity to the sequences in the databases. Sequence comparison among the assigned ORFs in the genome provided evidence that a considerable number of ORFs were generated by sequence duplication. By similarity search, 11 ORFs were assumed to contain the intein elements. The RNA genes identified were a single 16S-23S rRNA operon, two 5S rRNA genes and 46 tRNA genes including two with the intron structure. All the assigned ORFs and RNA coding regions occupied 91.25% of the whole genome. The data presented in this paper are available on the internet at http:@www.nite.go.jp.
Pyrococcus horikoshii hypothetical protein ph0594
