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Research Letters in Biochemistry
Volume 2009, Article ID 256124, 5 pages
Research Letter

Two Distantly Spaced Basic Patches in the Flexible Domain of Huntingtin-Interacting Protein 1 (HIP1) Are Essential for the Binding of Clathrin Light Chain

Department of Biology, Indiana University, Simon Hall 405B, 212 S. Hawthorne Drive, Bloomington, IN 47405, USA

Received 11 January 2009; Accepted 24 February 2009

Academic Editor: William S. Trimble

Copyright © 2009 Joel A. Ybe et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


The interaction between HIP family proteins (HIP1 and HIP12/1R) and clathrin is fundamental to endocytosis. We used circular dichroism (CD) to study the stability of an HIP1 subfragment (aa468-530) that is splayed open. CD thermal melts show HIP1 468-530 is only stable at low temperatures, but this HIP1 fragment contains a structural unit that does not melt out even at 83 C . We then created HIP1 mutants to probe our hypothesis that a short hydrophobic path in the opened region is the binding site for clathrin light chain. We found that the binding of hub/LCb was sensitive to mutating two distantly separated basic residues (K474 and K494). The basic patches marked by K474 and K494 are conserved in HIP12/1R. The lack of conservation in sla2p (S. cerevisiae), HIP1 from D. melanogaster, and HIP1 homolog ZK370.3 from C. elegans implies the binding of HIP1 and HIP1 homologs to clathrin light chain may be different in these organisms.