title: The structure of LL-diaminopimelate aminotransferase from Chlamydia trachomatis: implications for its broad substrate specificity.
abstract: We have previously reported the structures of the native holo and substrate-bound forms of LL-diaminopimelate aminotransferase from Arabidopsis thaliana (AtDAP-AT). Here, we report the crystal and molecular structures of the LL-diaminopimelate aminotransferase from Chlamydia trachomatis (CtDAP-AT) in the apo-form and the pyridoxal-5'-phosphate-bound form. The molecular structure of CtDAP-AT shows that its overall fold is essentially identical with that of AtDAP-AT except that CtDAP-AT adopts an "open" conformation as opposed to the "closed" conformation of AtDAP-AT. Although AtDAP-AT and CtDAP-AT are approximately 40% identical in their primary sequence, they have major differences in their substrate specificities; AtDAP-AT is highly specific for LL-DAP, whereas CtDAP-AT accepts a wider range of substrates. Since all of the residues involved in substrate recognition are highly conserved between AtDAP-AT and CtDAP-AT, we propose that differences in flexibility of the loops lining the active-site region between the two enzymes likely account for the differences in substrate specificity.
authors: Department of Biochemistry, University of Alberta, Edmonton, Alberta, Canada.
authors: Nobuhiko
authors: N
authors: Watanabe
authors: Matthew D
authors: MD
authors: Clay
authors: Marco J
authors: MJ
authors: van Belkum
authors: Chenguang
authors: C
authors: Fan
authors: John C
authors: JC
authors: Vederas
authors: Michael N G
authors: MN
authors: James
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism*; D020134:Catalytic Domain; D002692:Chlamydia trachomatis / Q000201:enzymology*; D003460:Crystallization; D018360:Crystallography, X-Ray; D008958:Models, Molecular; D015394:Molecular Structure; D011485:Protein Binding; D011487:Protein Conformation; D017510:Protein Folding; D013379:Substrate Specificity; D000637:Transaminases / Q000737:chemistry* / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; C561488:LL-diaminopimelate aminotransferase, Chlamydia trachomatis; D000637:Transaminases