• Title/Summary/Keyword: Direct target specificity of E2

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Direct characterization of E2-dependent target specificity and processivity using an artificial p27-linker-E2 ubiquitination system

  • Ryu, Kyoung-Seok;Choi, Yun-Seok;Ko, Jun-Sang;Kim, Seong-Ock;Kim, Hyun-Jung;Cheong, Hae-Kap;Jeon, Young-Ho;Choi, Byong-Seok;Cheong, Chae-Joon
    • BMB Reports
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    • v.41 no.12
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    • pp.852-857
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    • 2008
  • Little attention has been paid to the specificity between E2 and the target protein during ubiquitination, although RING-E3 induces a potential intra-molecular reaction by mediating the direct transfer of ubiquitin from E2 to the target protein. We have constructed artificial E2 fusion proteins in which a target protein (p27) is tethered to one of six E2s via a flexible linker. Interestingly, only three E2s (UbcH5b, hHR6b, and Cdc34) are able to ubiquitinate p27 via an intra-molecular reaction in this system. Although the first ubiquitination of p27 (p27-Ub) by Cdc34 is less efficient than that of UbcH5b and hHR6b, the additional ubiquitin attachment to p27-Ub by Cdc34 is highly efficient. The E2 core of Cdc34 provides specificity to p27, and the residues 184-196 are required for possessive ubiquitination by Cdc34. We demonstrate direct E2 specificity for p27 and also show that differential ubiquitin linkages can be dependent on E2 alone.