Ubiquitin Structure & Function: Difference between revisions
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The first step of ubiquitin activation involves the formation of a ubiqiotin-adenylate intermediate. This reaction requires an E1 ubiquitin-activating enzyme. The second step of ubiquitin activation transfers ubiquitin to the E1 active site cysteine residue and AMP is released. This step results in a thioester linkage between the C-terminal carboxyl group of ubiquitin and the E1 cysteine sulfhydryl group. | The first step of ubiquitin activation involves the formation of a ubiqiotin-adenylate intermediate. This reaction requires an E1 ubiquitin-activating enzyme. The second step of ubiquitin activation transfers ubiquitin to the E1 active site cysteine residue and AMP is released. This step results in a thioester linkage between the C-terminal carboxyl group of ubiquitin and the E1 cysteine sulfhydryl group. | ||
=== Ubiquitin Conjugation === | === Ubiquitin Conjugation === | ||
The activated ubiquitin in then transferred to a ubiquitin-conjugating enzyme, E2 through a trans-thiolesteration reaction. Ubiquitin is then transferred to the ε-amino group of a lysine chain on the target protein. An isopeptide bond is now formed between the carboxyl terminal of ubiquitin and the ε-amino group of the target protein lysine residue. This is accomplished by E2 directly. | |||
[[Image:diubq.png|350 px|center]] | [[Image:diubq.png|350 px|center]] | ||
Some proteins may be selected for degradation through the use of protein E3. E3 binds and catalyzes the isopeptide bond between ubiquitin and the target protein. Several activated ubiquitin may be added while still bound to E2 following the first ubiquitin addition. | |||
=== Proofreading === | === Proofreading === | ||
=== Conjugate Metabolism === | === Conjugate Metabolism === | ||
[[Image:Ubq_pathway.png|500 px|center]] | [[Image:Ubq_pathway.png|500 px|center]] | ||
<references/> | <references/> | ||
