Alternatively spliced exon B of myosin Va is essential for binding the tail-associated light chain shared by dynein.
A 10 kDa dynein light chain (DLC), previously identified as a tail light chain of myosin Va, may function as a cargo-binding and/or regulatory subunit of both myosin and dynein. Here, we identify and characterize the binding site of DLC on myosin Va. Fragments of the human myosin Va tail and the DLC2 isoform were expressed, and their complex formation was analyzed by pull-down assays, gel filtration, and spectroscopic methods. DLC2 was found to bind as a homodimer to a approximately 15 residue segment (Ile1280-Ile1294) localized between the medial and distal coiled-coil domains of the tail. The binding region contains the three residues coded by the alternatively spliced exon B (Asp1284-Lys1286). Removal of exon B eliminates DLC2 binding. Co-localization experiments in a transfected mammalian cell line confirm our finding that exon B is essential for DLC2 binding. Using circular dichroism, we demonstrate that binding of DLC2 to a approximately 85 residue disordered domain (Pro1235-Arg1320) induces some helical structure and stabilizes both flanking coiled-coil domains (melting temperature increases by approximately 7 degrees C). This result shows that DLC2 promotes the assembly of the coiled-coil domains of myosin Va. Nuclear magnetic resonance spectroscopy and docking simulations show that a 15 residue peptide (Ile1280-Ile1294) binds to the surface grooves on DLC2 similarly to other known binding partners of DLCs. When our data are taken together, they suggest that exon B and its associated DLC2 have a significant effect on the structure of parts of the coiled-coil tail domains and such a way could influence the regulation and cargo-binding function of myosin Va.
Hódi
Zsuzsa
Z
Department of Biochemistry, Eötvös Loránd University, Budapest, Hungary.
Németh
Attila L
AL
Radnai
László
L
Hetényi
Csaba
C
Schlett
Katalin
K
Bodor
Andrea
A
Perczel
András
A
Nyitray
László
L
D017398:Alternative Splicing; D000595:Amino Acid Sequence; D001665:Binding Sites / Q000235:genetics; D002352:Carrier Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D002942:Circular Dichroism; D029721:Drosophila Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D004398:Dyneins; D005091:Exons; D006801:Humans; D066298:In Vitro Techniques; D008958:Models, Molecular; D008969:Molecular Sequence Data; D046912:Multiprotein Complexes; D018995:Myosin Heavy Chains / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D024701:Myosin Type V / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D019906:Nuclear Magnetic Resonance, Biomolecular; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism
D002352:Carrier Proteins; D029721:Drosophila Proteins; D046912:Multiprotein Complexes; D011994:Recombinant Proteins; C077511:MYO5A protein, human; D024701:Myosin Type V; D018995:Myosin Heavy Chains; D004398:Dyneins