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Eukaryotic Cell, April 2005, p. 787-798, Vol. 4, No. 4
1535-9778/05/$08.00+0     doi:10.1128/EC.4.4.787-798.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.

A Point Mutation in the Cargo-Binding Domain of Myosin V Affects Its Interaction with Multiple Cargoes

Natasha Pashkova, Natalie L. Catlett,^, Jennifer L. Novak, and Lois S. Weisman^*

Department of Biochemistry, University of Iowa, Iowa City, Iowa

Received 20 December 2004/ Accepted 26 January 2005

Class V myosins move diverse intracellular cargoes, which attach via interaction of cargo-specific proteins to the myosin V globular tail. The globular tail of the yeast myosin V, Myo2p, contains two structural and functional subdomains. Subdomain I binds to the vacuole-specific protein, Vac17p, while subdomain II likely binds to an as yet unidentified secretory vesicle-specific protein. All functions of Myo2p require the tight association of subdomains I and II, which suggests that binding of a cargo to one subdomain may inhibit cargo-binding to a second subdomain. Thus, two types of mutations are predicted to specifically affect a subset of Myo2p cargoes: first are mutations within a cargo-specific binding region; second are mutations that mimic the inhibited conformation of one of the subdomains. Here we analyze a point mutation in subdomain I, myo2-2(G1248D), which is likely to be this latter type of mutation. myo2-2 has no effect on secretory vesicle movement. The secretory vesicle binding site is in subdomain II. However, myo2-2 is impaired in several Myo2p-related functions. While subdomains I and II of myo2-2p tightly associate, there are measurable differences in the conformation of its globular tail. Based solely on the ability to restore vacuole inheritance, a set of intragenic suppressors of myo2-2 were identified. All suppressor mutations reside in subdomain I. Moreover, subdomain I and II interactions occurred in all suppressors, demonstrating the importance of subdomain I and II association for Myo2p function. Furthermore, 3 of the 10 suppressors globally restored all tested defects in myo2-2. This large proportion of global suppressors strongly suggests that myo2-2(G1248) causes a conformational change in subdomain I that simultaneously affects multiple cargoes.

N.P. and N.L.C. contributed equally.

Present address: 737 Snapdragon St., Encinitas, CA 92024.

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