NMR Structural Mapping Reveals Promiscuous Interactions between Clathrin-Box Motif Sequences and the N-Terminal Domain of the Clathrin Heavy Chain.
Related Articles NMR Structural Mapping Reveals Promiscuous Interactions between Clathrin-Box Motif Sequences and the N-Terminal Domain of the Clathrin Heavy Chain.
Biochemistry. 2015 Apr 6;
Authors: Zhuo Y, Cano KE, Wang L, Ilangovan U, Hinck AP, Sousa R, Lafer EM
Abstract
Recruitment and organization of clathrin at endocytic sites to first form coated pits and then clathrin coated vesicles depends on interactions between the clathrin N-terminal domain (TD) and multiple clathrin binding sequences on the cargo adaptor and accessory proteins that concentrate at such sites. Up to four distinct protein binding sites have been proposed to be present on the clathrin TD, with each site proposed to interact with a distinct clathrin binding motif. However, an understanding of how such interactions contribute to clathrin coat assembly must take into account observations that any three of these four sites on clathrin TD can be mutationally ablated without causing loss of clathrin mediated endocytosis. In order to take an unbiased approach to mapping binding sites for clathrin box motifs on clathrin TD, we used isothermal titration calorimetry (ITC) and nuclear magnetic resonance (NMR) spectroscopy. Our ITC experiments revealed that a canonical clathrin box motif peptide from the AP-2 adaptor binds to clathrin TD with a stoichiometry of 3:1. Assignment of 90% of the total visible amide resonances in the Trosy-HSQC spectrum of (13)C, (2)H, (15)N-labelled TD40 allowed us to map these three binding sites by analyzing the chemical shift changes as clathrin box motif peptides were titrated into clathrin TD. We found that three different clathrin box motif peptides can each simultaneously bind not only to the previously characterized clathrin box site, but also to the W-box site and the ?-arrestin splice loop site on a single TD. The promiscuity of these binding sites can help explain why their mutation does not lead to larger effects on clathrin function and suggests a mechanism by which clathrin may be transferred between different proteins during the course of an endocytic event.
PMID: 25844500 [PubMed - as supplied by publisher]
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