Amino acid sequence of S-adenosyl-L-homocysteine hydrolase from rat liver as derived from the cDNA sequence.

Rat liver cDNA libraries constructed in lambda gt11 were screened for reactivity with polyclonal antibodies to native S-adenosyl-L-homocysteine (AdoHcy) hydrolase (adenosylhomocysteinase; EC 3.3.1.1). Five clones were isolated and sequenced. The amino acid sequence, deduced from the cDNA sequence, contained the sequence of eight peptides obtained by tryptic and cyanogen bromide fragmentation of rat liver AdoHcy hydrolase. Identification of the amino- and carboxyl-terminal peptides in the amino acid sequence showed that the complete sequence was obtained. A "fingerprint" sequence was found that is characteristic of dinucleotide-binding domains of many proteins. For AdoHcy hydrolase, this region from the lysine at position 213 to the aspartate at position 244, containing the sequence Gly-Xaa-Gly-Xaa-Xaa-Gly at positions 219-224, is presumably the site of binding for NAD+, which is required for the activity of the enzyme.