Structure and Organization of the hisA Gene of the Thermophilic Archaebacterium Methanococcus thermolithotrophicus

摘要

A restriction fragment of Methanococcus thermolithotrophicus genomic DNA was cloned into pUC8 to produce plasmid pET9301 which complements mutations in the hisA gene of Escherichia coli. Sequencing the DNA (2155bp) cloned from this thermophilic methanogen demonstrated that the M. thermolithotrophicus hisA gene is located within a cluster of open-reading frames (ORFs) and that this hisA gene is 68% and 69% homologous, at the nucleotide level, to the hisA genes of the mesophilic methanicocci, M. voltae and M. vanniellii. The ORF (ORF206) immediately 5' to the hisA gene of M. thermlothotrophicus is partially deleted in the genomes of the two mosophilic species, whereas ORF114 which is 5' to ORF206 is conserved in all three species. The M. thermollithotrophicus hisA gene product would be predicted, from its amino-acid sequence, to be more thermostable than the polypeptides encoded by the hisA genes of the mesophiles. Keywords: Genetics; Microbiology.