title: NAD-binding mode and the significance of intersubunit contact revealed by the crystal structure of Mycobacterium tuberculosis NAD kinase-NAD complex.
abstract: 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.
authors.affiliation: Department of Basic and Applied Molecular Biotechnology, Graduate School of Agriculture, Kyoto University, Uji, Kyoto 611-0011, Japan.
authors.forename: Shigetarou
authors.initials: S
authors.lastname: Mori
authors.forename: Masayuki
authors.initials: M
authors.lastname: Yamasaki
authors.forename: Yukie
authors.initials: Y
authors.lastname: Maruyama
authors.forename: Keiko
authors.initials: K
authors.lastname: Momma
authors.forename: Shigeyuki
authors.initials: S
authors.lastname: Kawai
authors.forename: Wataru
authors.initials: W
authors.lastname: Hashimoto
authors.forename: Bunzo
authors.initials: B
authors.lastname: Mikami
authors.forename: Kousaku
authors.initials: K
authors.lastname: Murata
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D018360:Crystallography, X-Ray; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009169:Mycobacterium tuberculosis / Q000201:enzymology*; D009243:NAD / Q000737:chemistry* / Q000378:metabolism*; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000737:chemistry* / Q000378:metabolism*; D011485:Protein Binding; D020836:Protein Structure, Quaternary; D021122:Protein Subunits / Q000737:chemistry / Q000378:metabolism; D016415:Sequence Alignment
chemical_list: D021122:Protein Subunits; D009243:NAD; D017853:Phosphotransferases (Alcohol Group Acceptor); C021844:NAD kinase