"Product of one of the 7 hmd co-occurring genes (hcg), hcgA-G, which cluster with the [Fe]-hydrogenase-encoding gene hmd and are required for the biosynthesis of the iron-guanylylpyridinol (FeGP) cofactor used by [Fe]-hydrogenase. HcgF catalyzes the transesterification of guanylylpyridinol-AMP produced by HcgE to afford a Cys(HcgF)-S-guanylylpyridinol thioester."xsd:string