A previously described regulatory effect of HypF mutatation is attributable to loss of activity of a regulatory hydrogenase. A zinc finger-like region CXXCX(18)CXXCX(24)CXXCX(18)CXXC region further supported the regulatory hypothesis. However, more recent work (PUBMED:11375153) shows the direct effect is on the activity of expressed hydrogenases with nickel/iron centers, rather than on expression. [Protein fate, Protein modification and repair]