Melanophilin Stimulates Myosin-5a Motor Function by Allosterically Inhibiting the Interaction between the Head and Tail of Myosin-5a.

Lin-Lin Yao,Yang Cao,Jie Zhang,Hai-Man Zhang,Qing-Juan Cao,Xiang-Dong Li

doi:10.1038/srep10874

Abstract

The tail-inhibition model is generally accepted for the regulation of myosin-5a motor function. Inhibited myosin-5a is in a folded conformation in which its globular tail domain (GTD) interacts with its head and inhibits its motor function, and high Ca2+ or cargo binding may reduce the interaction between the GTD and the head of myosin-5a, thus activating motor activity. Although it is well established that myosin-5a motor function is regulated by Ca2+, little is known about the effects of cargo binding. We previously reported that melanophilin (Mlph), a myosin-5a cargo-binding protein, is capable of activating myosin-5a motor function. Here, we report that Mlph-GTBDP, a 26 amino-acid-long peptide of Mlph, is sufficient for activating myosin-5a motor function. We demonstrate that Mlph-GTBDP abolishes the interaction between the head and GTD of myosin-5a, thereby inducing a folded-to-extended conformation transition for myosin-5a and activating its motor function. Mutagenesis of the GTD shows that the GTD uses two distinct, non-overlapping regions to interact with Mlph-GTBDP and the head of myosin-5a. We propose that the GTD is an allosteric protein and that Mlph allosterically inhibits the interaction between the GTD and head of myosin-5a, thereby activating myosin-5a motor function.

Highlights

Class V myosin (Myo5) is one of the oldest classes of myosins, which is distributed from lower eukaryotes, such as yeast, to vertebrate cells[1]
We found that Mlph-GTBDP, the 26-residue Myo5a-globular tail domain (GTD) binding peptide of Mlph identified by Spudich and colleagues[13], is capable of activating the motor function of Myo5a
We demonstrated that the binding of Mlph-GTBDP to the GTD inhibits the interaction between the GTD and head of Myo5a, disrupting the inhibition on the motor function in the head of Myo5a

Summary

Introduction

Class V myosin (Myo5) is one of the oldest classes of myosins, which is distributed from lower eukaryotes, such as yeast, to vertebrate cells[1]. Trybus and colleagues demonstrated at the single-molecule level that Mlph significantly increases the number of processively moving Myo5a molecules[26] It is not clear whether Mlph activates the Myo5a motor by the same mechanism as Ca2+; i.e., by abolishing the tail inhibition of the head. We found that Mlph-GTBDP, the 26-residue Myo5a-GTD binding peptide of Mlph identified by Spudich and colleagues[13], is capable of activating the motor function of Myo5a. We demonstrate that Mlph-GTBDP abolishes the interaction between the GTD and the head of Myo5a, inducing a folded-to-extended conformational transition of Myo5a and activating its motor function. We propose that the GTD of Myo5a is an allosteric protein and that Mlph-GTBDP binding allosterically inhibits the interaction between the GTD and the head of Myo5a, activating the head’s motor function

Methods

Results

Conclusion