SEQUENCE OF CDNA FOR RAT CYSTATHIONINE GAMMA-LYASE AND COMPARISON OF DEDUCED AMINO-ACID-SEQUENCE WITH RELATED ESCHERICHIA-COLI ENZYMES

A cDNA clone for cystathionine γ-lyase was isolated from a rat cDNA library in λ gt11 by screening with a monospecific antiserum. The identity of this clone, containing 600 bp proximal to the 3'-end of the gene, was confirmed by positive hybridization selection. Northern-blot hybridization showed the expected higher abundance of the corresponding mRNA in liver than in brain. Two further cDNA clones from a plasmid pcD library were isolated by colony hybridization with the first clone and were found to contain inserts of 1600 and 1850 bp. One of these was confirmed as encoding cystathionine γ-lyase by hybridization with two independent pools of oligodeoxynucleotides corresponding to partial amino acid sequence information for cystathionine γ-lyase. The other clone (estimated to represent all but 8% of the 5'-end of the mRNA) was sequenced and its deduced amino acid sequence showed similarity to those of the Escherichia coli enzymes cystathionine β-lyase and cystathionine γ-synthase throughout its length, especially to that of the latter.