Selective cysteine-to-selenocysteine changes in a [NiFe]-hydrogenase confirm a special position for catalysis and oxygen tolerance

• DOI: 10.1073/pnas.2100921118
• Publication Date: 2021-03-22T20:28:34Z
• Authors: Rhiannon M. Evans; Natalie Krahn; Bonnie J. Murphy; Harrison Lee; Fraser A. Armstrong; Dieter Söll
• Keywords: Oxygen; 0303 health sciences; 03 medical and health sciences; Amino Acid Substitution; Hydrogenase; Escherichia coli Proteins; Biocatalysis; Cysteine; Biological Sciences; Selenocysteine

Significance

Substitution of cysteine by selenocysteine is held responsible for the increased performance of many enzymes: The higher activity of [NiFeSe]-hydrogenases compared with their [NiFe] counterparts is often attributed to the Sec replacement of one active-site cysteine ligand. Replacing each of the four active-site cysteine residues in an O 2 -tolerant [NiFe]-hydrogenase by selenocysteine shows that this substitution alone does not overcome the inability to evolve H 2 that is a characteristic of the group 1d hydrogenases. A nonbridging cysteine lying on the direct path between the Ni and an adjacent proton-relaying glutamic acid emerges as being very special: Its substitution by selenocysteine confers extreme tolerance to O 2 but disrupts the proton transfer pathway, providing an example of where sulfur is superior to selenium.