title: Binding partners of the kinase domains in Drosophila obscurin and their effect on the structure of the flight muscle.
abstract: Drosophila obscurin (Unc-89) is a titin-like protein in the M-line of the muscle sarcomere. Obscurin has two kinase domains near the C-terminus, both of which are predicted to be inactive. We have identified proteins binding to the kinase domains. Kinase domain 1 bound Bällchen (Ball, an active kinase), and both kinase domains 1 and 2 bound MASK (a 400-kDa protein with ankyrin repeats). Ball was present in the Z-disc and M-line of the indirect flight muscle (IFM) and was diffusely distributed in the sarcomere. MASK was present in both the M-line and the Z-disc. Reducing expression of Ball or MASK by siRNA resulted in abnormalities in the IFM, including missing M-lines and multiple Z-discs. Obscurin was still present, suggesting that the kinase domains act as a scaffold binding Ball and MASK. Unlike obscurin in vertebrate skeletal muscle, Drosophila obscurin is necessary for the correct assembly of the IFM sarcomere. We show that Ball and MASK act downstream of obscurin, and both are needed for development of a well defined M-line and Z-disc. The proteins have not previously been identified in Drosophila muscle.
authors.affiliation: Department of Biology, University of York, York YO10 5DD, UK.
authors.forename: Anja
authors.initials: A
authors.lastname: Katzemich
authors.affiliation: Department of Biology, University of York, York YO10 5DD, UK.
authors.forename: Ryan J H
authors.initials: RJ
authors.lastname: West
authors.affiliation: King's College BHF Centre, Cardiovascular Division, London SE1 1UL, UK.
authors.forename: Atsushi
authors.initials: A
authors.lastname: Fukuzawa
authors.affiliation: Department of Biology, University of York, York YO10 5DD, UK.
authors.forename: Sean T
authors.initials: ST
authors.lastname: Sweeney
authors.affiliation: King's College BHF Centre, Cardiovascular Division, London SE1 1UL, UK.
authors.forename: Mathias
authors.initials: M
authors.lastname: Gautel
authors.affiliation: Department of Biology, University of York, York YO10 5DD, UK.
authors.forename: John
authors.initials: J
authors.lastname: Sparrow
authors.affiliation: Department of Biology, University of York, York YO10 5DD, UK belinda.bullard@york.ac.uk.
authors.forename: Belinda
authors.initials: B
authors.lastname: Bullard
mesh_terms: D000818:Animals; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000378:metabolism*; D004330:Drosophila / Q000502:physiology*; D029721:Drosophila Proteins / Q000737:chemistry / Q000378:metabolism*; D005426:Flight, Animal / Q000502:physiology*; D009124:Muscle Proteins / Q000737:chemistry / Q000378:metabolism*; D018482:Muscle, Skeletal / Q000378:metabolism* / Q000648:ultrastructure*; D006656:Protamine Kinase; D011485:Protein Binding; D054730:Protein Interaction Domains and Motifs; D011494:Protein Kinases / Q000737:chemistry / Q000378:metabolism*; D012518:Sarcomeres / Q000378:metabolism / Q000648:ultrastructure
chemical_list: D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; C582878:Mask protein, Drosophila; D009124:Muscle Proteins; C000608032:Unc-89 protein, Drosophila; D011494:Protein Kinases; C506651:Ball protein, Drosophila; D006656:Protamine Kinase
keywords: Ball; Drosophila; M-line; MASK; Obscurin; Unc-89