Crystal structure of Haemophilus influenzae NadR protein. A bifunctional enzyme endowed with NMN adenyltransferase and ribosylnicotinimide kinase activities

J Biol Chem. 2002 Sep 6;277(36):33291-9. doi: 10.1074/jbc.M204368200. Epub 2002 Jun 14.


Haemophilus influenzae NadR protein (hiNadR) has been shown to be a bifunctional enzyme possessing both NMN adenylytransferase (NMNAT; EC ) and ribosylnicotinamide kinase (RNK; EC ) activities. Its function is essential for the growth and survival of H. influenzae and thus may present a new highly specific anti-infectious drug target. We have solved the crystal structure of hiNadR complexed with NAD using the selenomethionine MAD phasing method. The structure reveals the presence of two distinct domains. The N-terminal domain that hosts the NMNAT activity is closely related to archaeal NMNAT, whereas the C-terminal domain, which has been experimentally demonstrated to possess ribosylnicotinamide kinase activity, is structurally similar to yeast thymidylate kinase and several other P-loop-containing kinases. There appears to be no cross-talk between the two active sites. The bound NAD at the active site of the NMNAT domain reveals several critical interactions between NAD and the protein. There is also a second non-active-site NAD molecule associated with the C-terminal RNK domain that adopts a highly folded conformation with the nicotinamide ring stacking over the adenine base. Whereas the RNK domain of the hiNadR structure presented here is the first structural characterization of a ribosylnicotinamide kinase from any organism, the NMNAT domain of hiNadR defines yet another member of the pyridine nucleotide adenylyltransferase family.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amino Acid Sequence
  • Bacterial Proteins*
  • Binding Sites
  • Crystallography, X-Ray
  • Haemophilus influenzae / metabolism*
  • Magnetic Resonance Spectroscopy
  • Models, Molecular
  • Models, Statistical
  • Molecular Sequence Data
  • Nicotinamide-Nucleotide Adenylyltransferase / metabolism*
  • Phosphotransferases (Alcohol Group Acceptor) / metabolism*
  • Protein Binding
  • Protein Conformation
  • Protein Structure, Tertiary
  • Repressor Proteins / chemistry*


  • Bacterial Proteins
  • NadR protein, bacteria
  • Repressor Proteins
  • Phosphotransferases (Alcohol Group Acceptor)
  • nicotinamide riboside kinase
  • Nicotinamide-Nucleotide Adenylyltransferase

Associated data

  • PDB/1LW7