The accessory sec system consisting of seven conserved components is commonly distributed among pathogenic Gram-positive bacteria for the secretion of serine-rich-repeat proteins (SRRPs). Asp1/2/3 protein complex in the system is responsible for both the O-acetylation of GlcNAc and delivering SRRPs to SecA2. However, the molecular mechanism of how Asp1/2/3 transport SRRPs remains unknown. Here, we report the complex structure of Asp1/2/3 from Streptococcus pneumoniae at 2.9 A. Further functional assays indicated that Asp1/2/3 can stimulate the ATPase activity of SecA2. In addition, the deletion of asp1/2/3 gene resulted in the accumulation of a secreted version of PsrP with an altered glycoform in protoplast fraction of the mutant cell, which suggested the modification/transport coupling of the substrate. Altogether, these findings not only provide structural basis for further investigations on the transport process of SRRPs, but also uncover the indispensable role of Asp1/2/3 in the accessory sec system.
The juvenile hormone (JH) epoxide hydrolase (JHEH) catalyzes the degradation of JH, which regulates the metamorphosis development of insects. Here we report the 2.30 A crystal structure of JHEH from the silkworm Bombyx mori (BmJHEH). The overall structure of BmJHEH is composed of an N-terminal segment followed by a core hydrolase domain, which is interrupted by an all-alpha lid domain. Structural analyses together with molecular simulation reveal insights into the conservation and specificity of the active-site pocket. These findings increase our understanding of the substrate recognition and catalysis of microsomal epoxide hydrolase family and might help the design of JH-derived pesticides. (c) Proteins 2014;. (c) 2014 Wiley Periodicals, Inc.
