Structure of the Functional Fragment of Auxilin Required for Catalytic Uncoating of Clathrin-Coated Vesicles

详细信息    查看全文

• 作者：James M. Gruschus ; Chae J. Han ; Tsvika Greener ; James A. Ferretti ; Lois E. Greene ; and ; and Evan Eisenberg
• 刊名：Biochemistry
• 出版年：2004
• 出版时间：March 23, 2004
• 年：2004
• 卷：43
• 期：11
• 页码：3111 - 3119
• 全文大小：534K
• 年卷期：v.43,no.11(March 23, 2004)
• ISSN：1520-4995

文摘

The three-dimensional structure of the C-terminal 20 kDa portion of auxilin, which consistsof the clathrin binding region and the C-terminal J-domain, has been determined by NMR. Auxilin is anHsp40 family protein that catalytically supports the uncoating of clathrin-coated vesicles through recruitmentof Hsc70 in an ATP hydrolysis-driven process. This 20 kDa auxilin construct contains the minimalsequential region required to uncoat clathrin-coated vesicles catalytically. The tertiary structure consistsof six helices, where the first three are unique to auxilin and believed to be important in the catalyticuncoating of clathrin. The last three helices correspond to the canonical J-domain of Hsp40 proteins. Thefirst helix, helix 1, which contains a conserved FEDLL motif believed to be necessary for clathrin binding,is transient and not packed against the rest of the structure. Helix 1 is joined to helix 2 by a flexiblelinker. Helix 2 packs loosely against the J-domain surface, whereas helix 3 packs tightly and makes criticalcontributions to the J-domain core. A long insert loop, also unique to the auxilin J-domain, is seen betweenhelix 4 and helix 5. Comparison with a previously reported structure of auxilin containing only helices3-6 shows a significant difference in the invariant HPD segment of the J-domain. The region wherehelix 1 is located corresponds to the expected region of the unstructured G/F-rich domain seen in DnaJ,i.e., the canonical N-terminal J-domain protein. In contrast, the location of helix 1 differs from the substratebinding regions of two other Hsp40 proteins, Escherichia coli Hsc20 and viral large T antigen. The varietyof biological functions performed by Hsp40 proteins such as auxilin, as well as the observed differencesin the structure and function of their substrate binding regions, supports the notion that Hsp40 proteinsact as target-specific adaptors that recruit their more general Hsp70 partners to specific biological roles.