Crystal structure of a type II dehydroquinate dehydratase-like protein from Bifidobacterium longum
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Dehydroquinate dehydratase (DHQD) catalyzes the third step in the biosynthetic shikimate pathway. Here we identify a Bifidobacterium longum protein with high sequence homology to type II DHQDs but no detectable DHQD activity under standard assay conditions. A crystal structure reveals that the B. longum protein adopts a DHQD-like tertiary structure but a distinct quaternary state. Apparently forming a dimer, the B. longum protein lacks the active site aspartic acid contributed from a neighboring protomer in the type II DHQD dodecamer. Relating to the absence of protein–protein interactions established in the type II DHQD dodecameric assembly, substantial conformational changes distinguish the would-be active site of the B. longum protein. As B. longum possess no other genes with homology to known DHQDs, these findings imply a unique DHQD activity within B. longum.
KeywordsPost-translational activation Quaternary structure Shikimate pathway X-ray crystal structure Structural genomics
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The Center for Structural Genomics of Infectious Diseases has been funded in whole or in part with federal funds from the National Institute of Allergy and Infectious Diseases, National Institutes of Health, Department of Health and Human Services, under contract nos. HHSN272200700058C and HHSN272201200026C. Use of the Advanced Photon Source was supported by the U. S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. Use of the LS-CAT Sector 21 was supported by the Michigan Economic Development Corporation and the Michigan Technology Tri-Corridor for the support of this research program (Grant 085P1000817).