Examination of key intermediates in the catalytic cycle of aspartate-beta-semialdehyde dehydrogenase from a gram-positive infectious bacteria.
Aspartate-beta-semialdehyde dehydrogenase (ASADH) catalyzes a critical branch point transformation in amino acid bio-synthesis. The products of the aspartate pathway are essential in microorganisms, and this entire pathway is absent in mammals, making this enzyme an attractive target for antibiotic development. The first structure of an ASADH from a Gram-positive bacterium, Streptococcus pneumoniae, has now been determined. The overall structure of the apoenzyme has a similar fold to those of the Gram-negative and archaeal ASADHs but contains some interesting structural variations that can be exploited for inhibitor design. Binding of the coenzyme NADP, as well as a truncated nucleotide analogue, into an alternative conformation from that observed in Gram-negative ASADHs causes an enzyme domain closure that precedes catalysis. The covalent acyl-enzyme intermediate was trapped by soaking the substrate into crystals of the coenzyme complex, and the structure of this elusive intermediate provides detailed insights into the catalytic mechanism.
Faehnle
Christopher R
CR
Department of Chemistry, University of Toledo, Toledo, Ohio 43606, USA.
Le Coq
Johanne
J
Liu
Xuying
X
Viola
Ronald E
RE
D001105:Archaea / Q000201:enzymology*; D001223:Aspartate-Semialdehyde Dehydrogenase / Q000737:chemistry*; D002151:Calorimetry; D002384:Catalysis; D020134:Catalytic Domain; D006094:Gram-Positive Bacteria / Q000201:enzymology*; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D013296:Streptococcus pneumoniae / Q000201:enzymology*; D013816:Thermodynamics
D001223:Aspartate-Semialdehyde Dehydrogenase