Removal of the C-terminal regulatory domain of α-isopropylmalate synthase disrupts functional substrate binding.

α-Isopropylmalate synthase (α-IPMS) catalyzes the metal-dependent aldol reaction between α-ketoisovalerate (α-KIV) and acetyl-coenzyme A (AcCoA) to give α-isopropylmalate (α-IPM). This reaction is the first committed step in the biosynthesis of leucine in bacteria. α-IPMS is homodimeric, with monomers consisting of (β/α)(8) barrel catalytic domains fused to a C-terminal regulatory domain, responsible for binding leucine and providing feedback regulation for leucine biosynthesis.

Excited state proton transfer in the red fluorescent protein mKeima.

mKeima is an unusual monomeric red fluorescent protein (lambda(em)(max) approximately 620 nm) that is maximally excited in the blue (lambda(ex)(max) approximately 440 nm). The large Stokes shift suggests that the chromophore is normally protonated. A 1.

Structures of the dimerization domains of the Escherichia coli disulfide-bond isomerase enzymes DsbC and DsbG.

DsbC and DsbG are periplasmic disulfide-bond isomerases, enzymes that facilitate the folding of secreted proteins with multiple disulfide bonds by catalyzing disulfide-bond rearrangement. Both enzymes also have in vitro chaperone activity. The crystal structures of these molecules are similar and both are V-shaped homodimeric modular structures.

Crystallization and preliminary X-ray analysis of alpha-isopropylmalate synthase from Mycobacterium tuberculosis.

alpha-Isopropylmalate synthase catalyses the aldol condensation of alpha-ketoisovalerate and acetyl coenzyme A to produce alpha-isopropylmalate. This reaction is the first committed step of leucine biosynthesis, which is interrelated with the pathways for production of the other branched-chain amino acids, valine and isoleucine. The absence of these pathways in mammals suggests that these enzymes could be useful targets for drug design against microbial pathogens.

Crystal structure of LeuA from Mycobacterium tuberculosis, a key enzyme in leucine biosynthesis.

The leucine biosynthetic pathway is essential for the growth of Mycobacterium tuberculosis and is a potential target for the design of new anti-tuberculosis drugs. The crystal structure of alpha-isopropylmalate synthase, which catalyzes the first committed step in this pathway, has been determined by multiwavelength anomalous dispersion methods and refined at 2.0-A resolution in complex with its substrate alpha-ketoisovalerate.