1m6s
From Proteopedia
Crystal Structure Of Threonine Aldolase
Overview
L-Threonine acetaldehyde-lyase (threonine aldolase, TA) is a pyridoxal-5'-phosphate-dependent (PLP) enzyme that catalyzes conversion of L-threonine or L-allo-threonine to glycine and acetaldehyde in a secondary glycine biosynthetic pathway. X-ray structures of Thermatoga maritima TA have been determined as the apo-enzyme at 1.8 A resolution and bound to substrate L-allo-threonine and product glycine at 1.9 and 2.0 A resolution, respectively. Despite low pairwise sequence identities, TA is a member of aspartate aminotransferase (AATase) fold family of PLP enzymes. The enzyme forms a 222 homotetramer with the PLP cofactor bound via a Schiff-base linkage to Lys199 within a domain interface. The structure reveals bound calcium and chloride ions that appear to contribute to catalysis and oligomerization, respectively. Although L-threonine and L-allo-threonine are substrates for T. maritima TA, enzymatic assays revealed a strong preference for L-allo-threonine. Structures of the external aldimines with substrate/product reveal a pair of histidines that may provide flexibility in substrate recognition. Variation in the threonine binding pocket may explain preferences for L-allo-threonine versus L-threonine among TA family members.
About this Structure
1M6S is a Single protein structure of sequence from Thermotoga maritima. Full crystallographic information is available from OCA.
Reference
X-ray structures of threonine aldolase complexes: structural basis of substrate recognition., Kielkopf CL, Burley SK, Biochemistry. 2002 Oct 1;41(39):11711-20. PMID:12269813 Page seeded by OCA on Sat May 3 00:42:16 2008
