Identification, Cloning, and Expression of the Gene for Adenylate Kinase from the Thermoacidophilic Archaebacterium Sulfolobus acidocaldarius

Abstract

An adenylate kinase gene from a member of the archaebacterial kingdom, the thermoacidophilic archaebacterium (archaeon) Sulfolobus acidocaldarius, has been cloned and sequenced for the first time. Two degenerate oligonucleotide probes, based on the N-terminal amino acid sequence information, led to the amplification of a gene-specific DNA fragment, used to screen subgenomic libraries. Comparing the DNA-derived amino acid sequence of total 194 residues with those of known procaryotic and eucaryotic adenylate kinases revealed only a low degree of similarity, except for a glycine-rich region close to the N-terminus, the so-called P-loop. Using inducible expression systems catalytically active S. acidocaldarius adenylate kinase was produced in large amounts. Although the total length of the protein and the results of alignment procedures suggest a closer relation to eucaryotic than to procaryotic sequences, the arcbaebacterial enzyme may represent a novel class of adenylate kinases. This is corroborated by the finding that an antiserum against this protein does not cross-react with Escherichia coli nor yeast or rabbit adenylate kinases for example.