title: Structures important in NAD(P)(H) specificity for mammalian retinol and 11-Cis-retinol dehydrogenases.
abstract: Mammalian retinol and 11-cis retinol dehydrogenases catalyze the formation of retinaldehyde from retinol and 11-cis retinaldehyde from 11-cis retinol, respectively. Although their amino acid sequences are 54% identical, these enzymes have different cofactor specificities: rat retinol dehydrogenase uses NADP+, while cow 11-cis retinol dehydrogenase uses NAD+. We used their close sequence similarity and the availability of 3D structures of their homologs to construct a 3D model of the two retinol dehydrogenases to investigate the determinants for cofactor specificity. The structure of rat retinol dehydrogenase shows that lysine-64 is important in stabilizing binding of 2'-phosphate on NADP+ in two ways: lysine's positively charged side chain has a coulombic attraction to the 2'-phosphate and partially compensates for the negative charge of aspartic acid-38. Cow 11-cis retinol dehydrogenase has threonine-61 at the position homologous to lysine-64. Threonine-61 does not have a stabilizing coulombic interaction with NADP+, nor can threonine-61 counteract the repulsive interaction between NADP+ and aspartic acid-37 in 11-cis retinol dehydrogenase. This suggests that aspartic acid-37 and threonine-61 are important in the specificity of 11-cis retinol dehydrogenase for NAD+.
authors.affiliation: Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla 92093, USA.
authors.forename: I
authors.initials: I
authors.lastname: Tsigelny
authors.forename: M E
authors.initials: ME
authors.lastname: Baker
mesh_terms: D000429:Alcohol Oxidoreductases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D000072467:Cytochrome P450 Family 2; D004563:Electrochemistry; D006801:Humans; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009243:NAD / Q000378:metabolism; D009249:NADP / Q000378:metabolism*; D010802:Phylogeny; D051381:Rats; D016415:Sequence Alignment; D013379:Substrate Specificity; D014801:Vitamin A / Q000737:chemistry / Q000378:metabolism*
chemical_list: D009243:NAD; D014801:Vitamin A; D009249:NADP; D000429:Alcohol Oxidoreductases; C022520:retinol dehydrogenase; C504568:Cyp2d1 protein, rat; D000072467:Cytochrome P450 Family 2