PMID: 22275129

Authors:

Dutta D, Bhattacharyya S, Das AK

Title:

Crystal structure and fluorescence studies reveal the role of helical dimeric interface of staphylococcal FabG1 in positive cooperativity for NADPH.

Journal:

Proteins. 2012 Jan 9. doi: 10.1002/prot.24024.

Abstract:

Crystal structure of Staphylococcal beta-ketoacyl-ACP reductase 1 (SaFabG1) complexed with NADPH is determined at 2.5 A resolution. The enzyme is essential in FAS-II pathway and utilizes NADPH to reduce beta-ketoacyl-ACP to (S)-beta-hydroxyacyl-ACP. Unlike the tetrameric FabGs, dimeric SaFabG1 shows positive homotropic cooperativity towards NADPH. Analysis of FabG:NADPH binary crystal structure endorses that NADPH interacts directly with the helices alpha4 and alpha5 those are present on a dimerization interface. A steady shift in tryptophan (of alpha4 helix) emission peak upon steady increment of NADPH concentration reveals that the dimeric interface is formed by alpha4-alpha4' and alpha5-alpha5' helices. This dimeric interface imparts positive homotropic cooperativity towards NADPH. PEG, a substrate mimicking molecule is also found near the active site of the enzyme. Proteins 2012. (c) 2012 Wiley-Liss, Inc.