No abstract

Lys-110 of human NADH-cytochrome b, reductase was replaced by Ala, Met, or Arg by site-directed mutagenesis to evaluate the role of the residue. K,,, values of purified Lys-110 -+ Ala and Lys-110 + Met mutants for NADH were approximately 200-fold and l,lOO-fold higher than that of the wild-type, respectively, while the value of the Arg mutant was almost the same as that of the wild-type. These results indicate that the positive charge at position 110 is important for NADH binding. The k,, value of Lys-110 -+ Ala was not affected, indicating that the residue only participates in the binding process in the reaction by forming an ionic interaction with phosphoryl group of NADH.NADH-cytochrome b, reductase; NADH binding; Site-directed mutagenesis