Sequence analysis of the L-lactate dehydrogenase-encoding gene of Deinococcus radiodurans, a suitable mesophilic counterpart for Thermus.

A gene encoding L-lactate dehydrogenase (LDH; EC 1.1.1.27) from Deinococcus radiodurans (Dr) was cloned and sequenced. The deduced amino acid (aa) sequence was compared to those of the Thermus aquaticus (Ta) and T. caldophilus (Tc) LDH. The similarity of the G + C contents between the Dr and Thermus genes permits the comparison of the aa sequences of LDH without considering the difference in the G + C contents. Compared to the mesophilic Dr LDH, increased numbers of hydrophobic aa, together with hydrophilic Arg, were found in the LDH from Ta and Tc, suggesting that these features would contribute to protein thermostability in part via hydrophobic and electrostatic interactions in the protein globule. Deinococcus would be a suitable mesophilic counterpart for Thermus to investigate the thermostability of proteins.