Moore J B, Markiewicz P, Miller J H
Department of Microbiology and Molecular Genetics, University of California Los Angeles 90024.
Gene. 1994 Sep 15;147(1):101-6. doi: 10.1016/0378-1119(94)90046-9.
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.
