The amino acids of proposed proton transfer pathway are highly conserved.

<p>T.r.: <i>Thiocapsa roseopersicina</i> HynL, A.v.: <i>Allochromatium vinosum</i> HydL, R.c.: <i>Rhodobacter capsulatus</i> HupL, M.c.: <i>Methylococcus capsulatus</i>, B.j.: <i>Bradyrhizobium japonicum</i> HupL, Rh.l.: <i>Rhizobium leguminosarum</i> HupL, R.e.: <i>Ralstonia eutropha</i> H16 HoxG, D.v.: <i>Desulfovibrio vulgaris</i> Miyazaki F HynB, D.g.: <i>Desulfovibrio gigas</i> HynB, D.f.: <i>Desulfovibrio fructosovorans</i> HynB. The upper and lower numbering refers to the large subunits of <i>T. roseopersicina</i> and <i>D. vulgaris</i> enzymes, respectively.</p

Bacterial strains.

<p>Indicated strains and plasmids are from Stratagene, La Jolla, CA, USA.</p

<i>In vivo</i> and <i>in vitro</i> hydrogenase activity of <i>Thiocapsa roseopersicina</i> HynSL enzyme.

<p><i>In vivo</i> and <i>in vitro</i> hydrogenase activity of <i>Thiocapsa roseopersicina</i> HynSL enzyme.</p

Vectors used in this study.

<p>Vectors used in this study.</p

Mutagenesis primers used for creating new mutants.

<p>Nucleotide triplets coding mutated amino acids are bold.</p

Arrangement of conserved histidines.

<p>T.r.: <i>Thiocapsa roseopersicina</i> HynL, A.v.: <i>Allochromatium vinosum</i> HydL, R.c.: <i>Rhodobacter capsulatus</i> HupL, M.c.: <i>Methylococcus capsulatus</i>, B.j.: <i>Bradyrhizobium japonicum</i> HupL, Rh.l.: <i>Rhizobium leguminosarum</i> HupL, R.e.: <i>Ralstonia eutropha</i> H16 HoxG, D.v.: <i>Desulfovibrio vulgaris</i> Miyazaki F HynB, D.g.: <i>Desulfovibrio gigas</i> HynB, D.f.: <i>Desulfovibrio fructosovorans</i> HynB. The numbering refers to the <i>T. roseopersicina</i> HynL subunit.</p