Structural insights into E1-catalyzed ubiquitin activation and transfer to conjugating enzymes.
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.
Lee
Imsang
I
Department of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, NY 11794-5215, USA.
Schindelin
Hermann
H
D018360:Crystallography, X-Ray; D008958:Models, Molecular; D017434:Protein Structure, Tertiary; D012441:Saccharomyces cerevisiae / Q000201:enzymology / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry* / Q000378:metabolism; D025801:Ubiquitin / Q000737:chemistry / Q000378:metabolism*; D044764:Ubiquitin-Activating Enzymes / Q000737:chemistry* / Q000378:metabolism
D029701:Saccharomyces cerevisiae Proteins; D025801:Ubiquitin; D044764:Ubiquitin-Activating Enzymes