InterPro domain: IPR042302

This domain is found in the ubiquitin-activating E1 (Ub-E1) family enzymes. It is one of the catalytic cysteine half-domains of Ub-E1. The catalytic cysteine half-domains contain the E1 active site cysteine, and are known as FCCH and SCCH, for 'first' and 'second' catalytic cysteine half-domain, respectively [ 1 , 2 ].

Structurally, the FCCH domain is composed of 7 anti-parallel beta sheets and 2 alpha helices.

1. Structural insights into E1-catalyzed ubiquitin activation and transfer to conjugating enzymes. Cell 134, 268-78
2. Crystal structure of a human ubiquitin E1-ubiquitin complex reveals conserved functional elements essential for activity. J Biol Chem 293, 18337-18352