Structural Insights Into E1-catalyzed Ubiquitin Activation and Transfer to Conjugating Enzymes

Cell. 2008 Jul 25;134(2):268-78. doi: 10.1016/j.cell.2008.05.046.

Abstract

Ubiquitin (Ub) and ubiquitin-like proteins (Ubls) are conjugated to their targets by specific cascades involving three classes of enzymes, E1, E2, and E3. Each E1 adenylates the C terminus of its cognate Ubl, forms a E1 approximately Ubl thioester intermediate, and ultimately generates a thioester-linked E2 approximately Ubl product. We have determined the crystal structure of yeast Uba1, revealing a modular architecture with individual domains primarily mediating these specific activities. The negatively charged C-terminal ubiquitin-fold domain (UFD) is primed for binding of E2s and recognizes their positively charged first alpha helix via electrostatic interactions. In addition, a mobile loop from the domain harboring the E1 catalytic cysteine contributes to E2 binding. Significant, experimentally observed motions in the UFD around a hinge in the linker connecting this domain to the rest of the enzyme suggest a conformation-dependent mechanism for the transthioesterification function of Uba1; however, this mechanism clearly differs from that of other E1 enzymes.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Crystallography, X-Ray
  • Models, Molecular
  • Protein Structure, Tertiary
  • Saccharomyces cerevisiae / enzymology
  • Saccharomyces cerevisiae / metabolism*
  • Saccharomyces cerevisiae Proteins / chemistry*
  • Saccharomyces cerevisiae Proteins / metabolism
  • Ubiquitin / chemistry
  • Ubiquitin / metabolism*
  • Ubiquitin-Activating Enzymes / chemistry*
  • Ubiquitin-Activating Enzymes / metabolism

Substances

  • Saccharomyces cerevisiae Proteins
  • Ubiquitin
  • Ubiquitin-Activating Enzymes

Associated data

  • PDB/3CMM