Originally published as Genetics Published Articles Ahead of Print on April 3, 2007.

Genetics, Vol. 176, 193-208, May 2007, Copyright © 2007
doi:10.1534/genetics.106.070300

The Biologically Relevant Targets and Binding Affinity Requirements for the Function of the Yeast Actin-Binding Protein 1 Src-Homology 3 Domain Vary With Genetic Context

Jennifer Haynes^*,, Bianca Garcia^*, Elliott J. Stollar^,, Arianna Rath, Brenda J. Andrews^*,,**,1 and Alan R. Davidson^*,

^* Department of Molecular and Medical Genetics, Terrence Donnelly Centre for Cellular and Biomolecular Research, Department of Biochemistry, and ^** Banting and Best Department of Medical Research, University of Toronto, Toronto, Ontario M5S 1A8, Canada and Structural Biology and Biochemistry, Hospital for Sick Children, Toronto, Ontario M5G 1X8, Canada

¹ Corresponding author: Terrence Donnelly Centre for Cellular and Biomolecular Research, University of Toronto, 160 College St., Toronto, ON M5S 3E1, Canada.
E-mail: brenda.andrews{at}utoronto.ca

Many protein–protein interaction domains bind to multiple targets. However, little is known about how the interactions of a single domain with many proteins are controlled and modulated under varying cellular conditions. In this study, we investigated the in vivo effects of Abp1p SH3 domain mutants that incrementally reduce target-binding affinity in four different yeast mutant backgrounds in which Abp1p activity is essential for growth. Although the severity of the phenotypic defects observed generally increased as binding affinity was reduced, some genetic backgrounds (prk1 and sla1) tolerated large affinity reductions while others (sac6 and sla2) were much more sensitive to these reductions. To elucidate the mechanisms behind these observations, we determined that Ark1p is the most important Abp1p SH3 domain interactor in prk1 cells, but that interactions with multiple targets, including Ark1p and Scp1p, are required in the sac6 background. We establish that the Abp1p SH3 domain makes different, functionally important interactions under different genetic conditions, and these changes in function are reflected by changes in the binding affinity requirement of the domain. These data provide the first evidence of biological relevance for any Abp1p SH3 domain-mediated interaction. We also find that considerable reductions in binding affinity are tolerated by the cell with little effect on growth rate, even when the actin cytoskeletal morphology is significantly perturbed.

This article has been cited by other articles:

				P. Vallurupalli, D. F. Hansen, E. Stollar, E. Meirovitch, and L. E. Kay Measurement of bond vector orientations in invisible excited states of proteins PNAS, November 20, 2007; 104(47): 18473 - 18477. [Abstract] [Full Text] [PDF]

International Access Link

Online ISS 1091-6490
Copyright 2008 by the Genetics Society of America
phone: 412-268-1812   fax: 412-268-1813   email: genetics-gsa{at}andrew.cmu.edu