Analysis of adenosine kinase mutants of baby hamster kidney cells using affinity-purified antibody.

The adenosine kinase enzymes from arabinofuranosyladenine-resistant (araAr) mutants of the baby hamster kidney cell line were analyzed using adenosine kinase-specific antibody probes purified by adenosine kinase-Sepharose column chromatography. Wild-type baby hamster kidney cells were shown to produce two adenosine kinase polypeptides of Mr 43,000 and 40,000. The class I araAr mutants that have no detectable adenosine kinase activity are completely deficient in the two adenosine kinase polypeptides. As expected, the class II araAr mutants, which had been shown to have an altered ribonucleotide diphosphate reductase activity, produce a wild-type level of the two adenosine kinase polypeptides. The five class III araAr mutants which are adenosine-sensitive (AdoS) have various levels of adenosine kinase activity and produced two adenosine kinase polypeptides with similar Mr as that of wild-type cells. The adenosine kinase proteins synthesized by two of the AdoS mutants, ara-19a and ara-74b, differed from wild type in their isoelectric points. These results plus the observations that the AdoS mutants produce adenosine kinase enzymes with altered kinetic properties suggest a point mutation in the adenosine kinase gene. An araAr mutant, ara-60a, with intermediate adenosine sensitivity, was shown to have two truncated adenosine kinase polypeptides. This observation strongly supports the genetic data which suggests that there is only one functional adenosine kinase allele in baby hamster kidney cells and that the two adenosine kinase polypeptides are due to posttranscriptional modification.