Identification of a Minimal Myosin Va Binding Site within an Intrinsically Unstructured Domain of Melanophilin

101

Class V myosins (MyoV), the most studied unconventional myosins, recognize numerous cargos mainly via the motor's globular tail domain (GTD). Little is known regarding how MyoV-GTD recognizes such a diverse array of cargos specifically. Here, we solved the crystal structures of MyoVa-GTD in its apo-form and in complex with two distinct cargos, melanophilin and Rab interacting lysosomal protein-like 2. The apo-MyoVa-GTD structure indicates that most mutations found in patients with Griscelli syndrome, microvillus inclusion disease, or cancers or in "dilute" rodents likely impair the folding of GTD. The MyoVa-GTD/cargo complex structure reveals two distinct cargo-binding surfaces, one primarily via charge-charge interaction and the other mainly via hydrophobic interactions. Structural and biochemical analysis reveal the specific cargo-binding specificities of various isoforms of mammalian MyoV as well as very different cargo recognition mechanisms of MyoV between yeast and higher eukaryotes. The MyoVa-GTD structures resolved here provide a framework for future functional studies of vertebrate class V myosins.

Section: Myova-gtd Uses Different Sites To Interact With Rilpl2 and Msupporting

confidence: 91%

Section: Myova-gtd Uses Different Sites To Interact With Rilpl2 and Mmentioning

confidence: 99%

Structural basis of cargo recognitions for class V myosins

Wei

Liu

et al. 2013

101

“…MLPH has two independent Myo5A-binding domains (32,33). The MLPH domain (residues 320-406), that binds the melanosomespecific Myo5A exon-F region upstream of the GTD, appears to be required for Myo5A recruitment to and transport of melanosomes (34) and is thus critical for the specificity of this recruitment.…”

Section: Structural Recognition Of the Mlph By An Isoform-specific Bimentioning

confidence: 99%

Structural basis of myosin V Rab GTPase-dependent cargo recognition

Pylypenko

Attanda

Gauquelin

et al. 2013

108

Specific recognition of the cargo that molecular motors transport or tether to cytoskeleton tracks allows them to perform precise cellular functions at particular times and positions in cells. However, very little is known about how evolution has favored conservation of functions for some isoforms, while also allowing for the generation of new recognition sites and specialized cellular functions. Here we present several crystal structures of the myosin Va or the myosin Vb globular tail domain (GTD) that gives insights into how the motor is linked to the recycling membrane compartments via Rab11 or to the melanosome membrane via recognition of the melanophilin adaptor that binds to Rab27a. The structures illustrate how the Rab11-binding site has been conserved during evolution and how divergence at another site of the GTD allows more specific interactions such as the specific recognition of melanophilin by the myosin Va isoform. With atomic structural insights, these structures also show how either the partner or the GTD structural plasticity upon association is critical for selective recruitment of the motor.GTPases | DIL motif | Rab effector | intracellular traffic D irected movement is essential for life, and cytoskeletonbased motors generate mechanical force and motion to precisely organize the cell. Their coordinated actions allow them to play key roles in nearly every physiological process. Class V myosins (Myo5) and the related plant class XI myosins are a group of multifunctional actin-based nanomotors that have evolved from one of the three ancient myosin subfamilies (1). The motor domain and extended lever arm of these myosins is followed by a coiled coil dimerizing region and the C-terminal globular tail domain (GTD) that primarily plays a role in selective cargo recruitment. Little is known, however, about how this GTD sequence has evolved to serve both a role in regulation of the motor activity (2, 3) and specific recruitment of the motor, which is critical to control precisely in space and time when the motor is activated for different cellular functions.

“…For those classes of myosin that dimerize, a helical dimerization module follows the lever arm region. Finally, the C terminus end contains a distinct tail region for binding either to distinct cargo molecules (4,5) or, in the case of muscle myosins, to associate into myosin filaments.…”

mentioning

confidence: 99%

UNC-45/CRO1/She4p (UCS) protein forms elongated dimer and joins two myosin heads near their actin binding region

Shi

Blobel

2010

UNC-45/CRO1/She4p (UCS) proteins have variously been proposed to affect the folding, stability, and ATPase activity of myosins. They are the only proteins known to interact directly with the motor domain. To gain more insight into UCS function, we determined the atomic structure of the yeast UCS protein, She4p, at 2.9 Å resolution. We found that 16 helical repeats are organized into an L-shaped superhelix with an amphipathic N-terminal helix dangling off the short arm of the L-shaped molecule. In the crystal, She4p forms a 193-Å-long, zigzag-shaped dimer through three distinct and evolutionary conserved interfaces. We have identified She4p’s C-terminal region as a ligand for a 27-residue-long epitope on the myosin motor domain. Remarkably, this region consists of two adjacent, but distinct, binding epitopes localized at the nucleotide-responsive cleft between the nucleotide- and actin-filament-binding sites. One epitope is situated inside the cleft, the other outside the cleft. After ATP hydrolysis and Pi ejection, the cleft narrows at its base from 20 to 12 Å thereby occluding the inside the cleft epitope, while leaving the adjacent, outside the cleft binding epitope accessible to UCS binding. Hence, one cycle of higher and lower binding affinity would accompany one ATP hydrolysis cycle and a single step in the walk on an actin filament rope. We propose that a UCS dimer links two myosins at their motor domains and thereby functions as one of the determinants for step size of myosin on actin filaments.