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Publication Abstract from PubMed

NAD kinase is a key enzyme in NADP biosynthesis. We solved the crystal structure of polyphosphate/ATP-NAD kinase from Mycobacterium tuberculosis (Ppnk) complexed with NAD (Ppnk-NAD) at 2.6A resolution using apo-Ppnk structure solved in this work, and revealed the details of the structure and NAD-binding site. Superimposition of tertiary structures of apo-Ppnk and Ppnk-NAD demonstrated a substantial conformational difference in a loop (Ppnk-flexible loop). As a quaternary structure, these Ppnk structures exhibited tetramer as in solution condition. Notably, the Ppnk-flexible loop was involved in the intersubunit contact and probably related to the NAD-binding of the other subunit. Furthermore, the two residues (Asp189, His226) substantially contributed to creating NAD-binding site on the other subunit. The two residues and the residues involved in NAD-binding were conserved. However, residues corresponding to the Ppnk-flexible loop were not conserved, making us to speculate that the Ppnk-flexible loop may be Ppnk-specific.

NAD-binding mode and the significance of intersubunit contact revealed by the crystal structure of Mycobacterium tuberculosis NAD kinase-NAD complex.,Mori S, Yamasaki M, Maruyama Y, Momma K, Kawai S, Hashimoto W, Mikami B, Murata K Biochem Biophys Res Commun. 2005 Feb 11;327(2):500-8. PMID:15629142^[3]

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