selH

selH is a gene found in bacteria, notably in species like *Escherichia coli*. It encodes a protein that is part of the selenocysteine biosynthesis pathway. Specifically, selH is involved in the reduction of selenophosphate to selenide. This reduction step is crucial for the synthesis of the amino acid selenocysteine, which is the 21st amino acid incorporated into proteins. Selenocysteine has unique redox properties and is found in the active sites of various enzymes involved in antioxidant defense and other metabolic processes.

The selH protein belongs to the thioredoxin reductase family, suggesting it utilizes a redox mechanism to carry out its function. The enzyme contains a CXXC motif, which is characteristic of thioredoxin fold proteins and is essential for its catalytic activity. The accurate synthesis of selenocysteine is vital for the proper function of selenoproteins, and thus selH plays an indirect but critical role in cellular metabolism and survival. Mutations or disruptions in the selH gene can lead to a deficiency in selenocysteine biosynthesis, impacting the organisms that rely on this pathway.