Biosynthesis of the Selenium-Substituted [FeFe]-Hydrogenases

High Resolution Image Download MS PowerPoint Slide The [FeFe]-hydrogenase from Chlamydomonas reinhardtii ( Cr HydA1) has been prepared with Se in place of S at the [2Fe] H active site by HydF-mediated maturation using [HFe 2 (μ-SeH)(μ-Se)(CN) 2 (CO) 4 ] 2– ([ 2 ] 2– ) and the apoenzyme. Complex [ 2 ] 2– is a hydride─a rare case where a metalloselenol and the (naturally occurring) metallothiol [Fe 2 (μ-SH) 2 (CN) 2 (CO) 4 ] 2– ─adopt different structures. The structure of [ 2 ] 2– was deduced based on 1 H and 77 Se NMR spectroscopy. From [ 2 ] 2–, highly active Cr HydA1-Se 2 can be efficiently produced using CH 2 O, but not serine, as the precursor to the azadiselenolate cofactor. EPR/ENDOR spectroscopic studies were corroborated with isotopically pure Cr HydA1- 77 Se 2 produced by maturation with [Fe 2 [(μ- 77 SeCH 2 ) 2 NH](CN) 2 (CO) 4 ] 2– . Cr HydA1-Se 2 and native Cr HydA1 have distinct, but quite similar geometric and electronic structures and redox properties.