Molecular Chaperones, Cochaperones, and Ubiquitination/Deubiquitination System: Involvement in the Production of High Quality Spermatozoa
Figure 1
(a) The addition of ubiquitin at specific lysine residues on target protein requires the sequential activity of ubiquitin activating enzyme E1, ubiquitin conjugating enzyme E2, and ubiquitin ligase E3. (b) Different ubiquitin pathways: the addition of a chain of four ubiquitin molecules via lysine 48 in target protein is a tag for degradation into the proteasome; the addition of polyubiquitin chain via lysine 63 and multiubiquitin and monoubiquitin addition in target proteins activate cellular events other than proteasome dependent degradation (part of this figure was modified from [18]).
