Sandbox 820

The <scene name='69/695713/Uba1/1'>monomeric structure</scene> of Uba1 consists of six structural domains (IAD, AAD, FCCH, SCCH, 4HB, and UFD), four of which pack together to create a central canyon. <ref/> Lee I, Schindelin H. Structural Insights into E1-Catalyzed Ubiquitin Activation and Transfer to Conjugating Enzymes. Cell 134, 268–278 (2008).<ref> The canyon is divided into two distinct clefts (left and right) by the SCCH/AAD linker fragment.{Lee, 2008} Ubiquitin binds to the cysteine located on the right cleft of Uba1 which allows for Ubiquitin to orient itself relative to the active site located on the left cleft.{Lee, 2008} The structure of <scene name='69/695713/Uba1_monomeric_ub/2'>Ubiquitin bound to Uba1</scene> results in a change in conformation that buries a significant portion of Uba1 exposed surface area.{Lee, 2008} The catalytic cysteine located on the SCCH domain of Uba1 forms a thioester with the C-terminus of Ubiquitin, forming a <scene name='69/695713/Uba1_monomeric_ub_catcys_hi/1'>thioester complex</scene>.{Lee, 2008} It is suggested that a significant conformation change occurs when Ubiquitin binds to Uba1 due to the large distance (~35 Å) between the catalytic cysteine residue and the adenylation active site.{Lee, 2008; Walden, 2003}