title: Crystal structures of Cg1458 reveal a catalytic lid domain and a common catalytic mechanism for the FAH family.
abstract: Cg1458 was recently characterized as a novel soluble oxaloacetate decarboxylase. However, sequence alignment identified that Cg1458 has no similarity with other oxaloacetate decarboxylases and instead belongs to the FAH (fumarylacetoacetate hydrolase) family. Differences in the function of Cg1458 and other FAH proteins may suggest a different catalytic mechanism. To help elucidate the catalytic mechanism of Cg1458, crystal structures of Cg1458 in both the open and closed conformations have been determined for the first time up to a resolution of 1.9 Å (1 Å=0.1 nm) and 2.0 Å respectively. Comparison of both structures and detailed biochemical studies confirmed the presence of a catalytic lid domain which is missing in the native enzyme structure. In this lid domain, a glutamic acid-histidine dyad was found to be critical in mediating enzymatic catalysis. On the basis of structural modelling and comparison, as well as large-scale sequence alignment studies, we further determined that the catalytic mechanism of Cg1458 is actually through a glutamic acid-histidine-water triad, and this catalytic triad is common among FAH family proteins that catalyse the cleavage of the C-C bond of the substrate. Two sequence motifs, HxxE and Hxx…xxE have been identified as the basis for this mechanism.
authors.affiliation: Key Laboratory of Microbiological Engineering of Agricultural Environment, Ministry of Agriculture, Department of Microbiology, College of Life Sciences, Nanjing Agricultural University, 210095 Nanjing, China.
authors.forename: Tingting
authors.initials: T
authors.lastname: Ran
authors.forename: Yanyan
authors.initials: Y
authors.lastname: Gao
authors.forename: May
authors.initials: M
authors.lastname: Marsh
authors.forename: Wenjun
authors.initials: W
authors.lastname: Zhu
authors.forename: Meitian
authors.initials: M
authors.lastname: Wang
authors.forename: Xiang
authors.initials: X
authors.lastname: Mao
authors.forename: Langlai
authors.initials: L
authors.lastname: Xu
authors.forename: Dongqing
authors.initials: D
authors.lastname: Xu
authors.forename: Weiwu
authors.initials: W
authors.lastname: Wang
mesh_terms: D001426:Bacterial Proteins / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000235:genetics; D002262:Carboxy-Lyases / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000235:genetics; D002384:Catalysis; D020134:Catalytic Domain / Q000235:genetics; D048230:Corynebacterium glutamicum / Q000201:enzymology* / Q000235:genetics; D018360:Crystallography, X-Ray; D018698:Glutamic Acid / Q000737:chemistry / Q000378:metabolism; D006639:Histidine / Q000737:chemistry / Q000378:metabolism; D006867:Hydrolases / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000235:genetics; D005810:Multigene Family; D020125:Mutation, Missense; D011487:Protein Conformation; D016963:Thermus thermophilus / Q000201:enzymology / Q000235:genetics; D014169:Transformation, Bacterial / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; D018698:Glutamic Acid; D006639:Histidine; D006867:Hydrolases; C020156:fumarylacetoacetase; D002262:Carboxy-Lyases; C021916:oxaloacetate decarboxylase