4dpk

Publication Abstract from PubMed

Autotrophic members of the Sulfolobales (crenarchaeota) use the 3-hydroxypropionate/4-hydroxybutyrate cycle to assimilate CO2 into cell material. The product of the initial acetyl-CoA carboxylation with CO2, malonyl-CoA, is further reduced to malonic semialdehyde by an NADPH-dependent malonyl-CoA reductase (MCR); the enzyme also catalyzes the reduction of succinyl-CoA to succinic semialdehyde onwards in the cycle. Here, we present the crystal structure of Sulfolobus tokodaii malonyl-CoA reductase in the substrate-free state and in complex with NADP+ and CoA. Structural analysis revealed an unexpected reaction cycle in which NADP+ and CoA successively occupy identical binding sites. Both coenzymes are pressed into a S-shaped, nearly superimposable structure imposed by a fixed and preformed binding site. The template-governed cofactor shaping implicates the same binding site for the 3- and 2- ribose phosphate group of CoA and NADP+, respectively, but a different one for the common ADP part: the beta-phosphate of CoA aligns with the alpha-phosphate of NADP+. Evolution from an NADP+ to a bispecific NADP+ and CoA binding site involves many amino acid exchanges within a complex process by which constraints of the CoA structure also influence NADP+ binding. Based on the paralogous aspartate-semialdehyde dehydrogenase structurally characterized with a covalent Cys-aspartyl adduct, a malonyl/succinyl group can be reliably modelled into MCR and discussed regarding its binding mode, the malonyl/succinyl specificity, and the catalyzed reaction. The modified polypeptide surrounding around the absent ammonium group in malonate/succinate compared to aspartate provides the structural basis for engineering a methylmalonyl-CoA reductase applied for biotechnical polyester building block synthesis.

Structural basis for a bispecific NADP+ and CoA binding site in an archaeal malonyl-coenzyme A reductase.,Demmer U, Warkentin E, Srivastava A, Kockelkorn D, Poetter M, Marx A, Fuchs G, Ermler U J Biol Chem. 2013 Jan 16. PMID:23325803^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.