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The gene for the Thermotoga maritima Trk potassium transporter component TrkA was originally thought to be a frameshift mutation and not to encode a functional protein. However, expression from this gene yielded a complex consisting of two distinct proteins designated TM1088A and -B. Genetic complementation of Escherichia coli mutants unable to transport potassium suggests that TM1088A/B is part of a functional Trk potassium transporter complex with the membrane protein TM1089. The protein structure for TM1088A shows a characteristic Rossmann fold indicating an [NAD.sup.+] binding site and has structural similarity to potassium channel-related proteins. Ligand binding studies indicated that ATP, ADP, and AMP stabilized TM1088A to a much greater degree than NADH and NAD, consistent with the crystal structure of TM1088A, which contains a bound AMP natural ligand at the characteristic GXGXXG nucleotide binding site. Mutation of single and all glycines at this nucleotide binding site eliminated in vitro protein stabilization by the ligand, yet these mutated proteins could still functionally complement the E. coli potassium uptake mutants. We predict that this new two-subunit class of TrkA proteins is present in a number of organisms. A further subclass of the predicted two-subunit TrkA proteins lack an identifiable membrane-spanning subunit of the Trk [K.sup.+] transporter. This class, as exemplified by Mycobacterium tuberculosis, did not complement E. coli potassium transport with the native E. coil TrkH; thus, it may require a novel TrkH-like protein for activity or provide an alternate function in vivo.

The anaerobic ethylbenzene dehydrogenase is a heterodimer and oxidizes 4-fluro-ethylbenzene and the non-aromatic hydrocarbons. Gene sequence data reveal that ebdA, ebdb, and ebdC encode the alpha-, beta-, and gamma-subunits, respectively. The alpha and beta subunits bind molybdopterin and 4Fe-4S whereas the gamma subunit functions as a membrane anchor domain.

Research is conducted on the in vitro characterization of anaerobic ethylbenzene mineralization enzymes ethylbenzene dehydrogenase and 1-phenylethanol dehydrogenase in bacterium Azoarcus sp.strain EB1. The presence of both enzymes in cells grown on 1-phenylethanol and acetophenone substrate is described.

Genomic insights into Mn(II) oxidation by the marine alphaproteobacterium Aurantimonas sp. strain S185-9A1, which are isolated from the oxic/anoxic interface of a stratified fjord, are described. The results have provided insights into the physiology and biochemistry of Mn(II) oxidation and have disclosed a genome specialized for life at the oxic/anoxic interface.

Investigates the initial reactions in anaerobic oxidation of ethylbenzene in a denitrifying bacterium, strain EB1. Enrichment and isolation of strain EB1; Phylogenetic position of the strain; Anaerobic mineralization of ethylbenzene; Carbon dioxide dependence of acetophenone degradation.