Biomedical subjects

Natasha Pashkova

Publications and source records attributed to Natasha Pashkova.

3 recordsLinked to original sources

PubMed2006

Structural basis for myosin V discrimination between distinct cargoes.

Myosin V molecular motors move cargoes on actin filaments. A myosin V may move multiple cargoes to distinct places at different times. The cargoes attach to the globular tail of myosin V via cargo-specific receptors. Here we report the crystal structure at 2.2 A of the myosin V globular tail. The overall tertiary structure has not been previously observed. There are several patches of highly conserved regions distributed on the surface of the tail. These are candidate attachment sites for cargo-specific receptors. Indeed, we identified a region of five conserved surface residues that are solely required for vacuole inheritance. Likewise, we identified a region of five conserved surface residues that are required for secretory vesicle movement, but not vacuole movement. These two regions are at opposite ends of the oblong-shaped cargo-binding domain, and moreover are offset by 180 degrees. The fact that the cargo-binding areas are distant from each other and simultaneously exposed on the surface of the globular tail suggests that major targets for the regulation of cargo attachment are organelle-specific myosin V receptors.

Biological Transport, Active↗

PubMed2005

Myosin V attachment to cargo requires the tight association of two functional subdomains.

The myosin V carboxyl-terminal globular tail domain is essential for the attachment of myosin V to all known cargoes. Previously, the globular tail was viewed as a single, functional entity. Here, we show that the globular tail of the yeast myosin Va homologue, Myo2p, contains two structural subdomains that have distinct functions, namely, vacuole-specific and secretory vesicle-specific movement. Biochemical and genetic analyses demonstrate that subdomain I tightly associates with subdomain II, and that the interaction does not require additional proteins. Importantly, although neither subdomain alone is functional, simultaneous expression of the separate subdomains produces a functional complex in vivo. Our results suggest a model whereby intramolecular interactions between the globular tail subdomains help to coordinate the transport of multiple distinct cargoes by myosin V.

Amino Acid Sequence↗

PubMed2005

A point mutation in the cargo-binding domain of myosin V affects its interaction with multiple cargoes.

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.

Binding Sites↗