Identification and sequencing of the Thermotoga maritima lacZ gene, part of a divergently transcribed operon.
The lacZ gene encoding a beta-galactosidase (beta Gal) from the hyperthermophile Thermotoga maritima was cloned on an 11-kb fragment by complementation of an Escherichia coli lacZ deletion stain. The nucleotide sequence of the structural gene and two other ORFs found within a 6317-bp region were determined. The deduced amino acid (aa) sequence of the Tt. maritima beta Gal predicts a 1037-aa polypeptide with a calculated M(r) of 122,312. The translated sequence is 30% similar to nine other beta Gal sequences from bacteria and one yeast. Alignment of the Tt. maritima beta Gal with these other sequences reveals that the residues responsible for Mg2+ binding, catalysis and substrate recognition are conserved in the thermophilic enzyme. Sequence analysis also revealed the presence of a divergently transcribed operon containing at least two other genes 5' to lacZ. These ORFs encode proteins homologous to a second family of beta Gal found in Bacillus species and to an ATP-dependent family of bacterial oligopeptide transport proteins.
Moore
J B
JB
Department of Microbiology and Molecular Genetics, University of California Los Angeles 90024.
Markiewicz
P
P
Miller
J H
JH
D000595:Amino Acid Sequence; D001483:Base Sequence; D002462:Cell Membrane / Q000378:metabolism; D003001:Cloning, Molecular; D005798:Genes, Bacterial; D006089:Gram-Negative Anaerobic Bacteria / Q000235:genetics*; D006358:Hot Temperature; D007763:Lac Operon; D008969:Molecular Sequence Data; D016366:Open Reading Frames; D010802:Phylogeny; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D014158:Transcription, Genetic; D001616:beta-Galactosidase / Q000235:genetics*
D001616:beta-Galactosidase