The cell shape-determining Csd6 protein from Helicobacter pylori constitutes a new family of L, D-carboxypeptidase

Hyoun Sook Kim, Ha Na Im, Doo Ri An, Ji Young Yoon, Jun Young Jang, Shahriar Mobashery, Dusan Hesek, Mijoon Lee, Jakyung Yoo, Minghua Cui, Sun Choi, Cheolhee Kim, Nam Ki Lee, Soon Jong Kim, Jin Young Kim, Geul Bang, Byung Woo Han, Byung Il Lee, Hye Jin Yoon, Se Won Suh

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26 Scopus citations


Helicobacter pyloricauses gastrointestinal diseases, including gastric cancer. Its high motility in the viscous gastric mucosa facilitates colonization of the human stomach and depends on the helical cell shape and the flagella. In H. pylori, Csd6 is one of the cell shape-determining proteins that play key roles in alteration of cross-linking or by trimming of peptidoglycan muropeptides. Csd6is also involved in deglycosylation of the flagellar protein FlaA. To better understand its function, biochemical, biophysical, and structural characterizations were carried out. We show that Csd6 has a three-domain architecture and exists asadimerinsolution. The N-terminal domain playsakey role in dimerization. The middle catalytic domain resembles those of L, D-transpeptidases, but its pocket-shaped active site isuniquely defined by the four loops I to IV, among which loops I and III show the most distinct variations from the known L, D-transpeptidases. Mass analyses confirm that Csd6 functions only as an L, D-carboxypeptidase and not as an L, D-transpeptidase. The D-Ala-complexed structure suggests possible binding modes of both the substrate and product to the catalytic domain. The C-terminal nuclear transport factor 2-like domain possesses a deep pocket for possible binding of pseudaminic acid, and in silicodocking supports its roleindeglycosylationofflagellin. On the basis of these findings, it is proposed that H. pylori Csd6 and its homologs constitute a new family of L, D-carboxypeptidase. This work provides insights into the function of Csd6 in regulating the helical cell shape and motility of H. pylori.

Original languageEnglish
Pages (from-to)25103-25117
Number of pages15
JournalJournal of Biological Chemistry
Issue number41
StatePublished - 9 Oct 2015

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© 2015 by The American Society for Biochemistry and Molecular Biology, Inc.


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