Iron hydrogenase, subset <p> This model describes iron-only hydrogenases of anaerobic and microaerophilic bacteria and protozoa. These proteins represent a subdivision within a larger family which includes proteins such as nuclear prelamin A recognition factor in animals. These proteins show some heterogeneity in terms of periplasmic, cytosolic or hydrogenosomic location, NAD or NADP dependence, and overall protein length.</p>