Two regions of the tail are necessary for the isoform-specific functions of nonmuscle myosin IIB.
To function in the cell, nonmuscle myosin II molecules assemble into filaments through their C-terminal tails. Because myosin II isoforms most likely assemble into homo-filaments in vivo, it seems that some self-recognition mechanisms of individual myosin II isoforms should exist. Exogenous expression of myosin IIB rod fragment is thus expected to prevent the function of myosin IIB specifically. We expected to reveal some self-recognition sites of myosin IIB from the phenotype by expressing appropriate myosin IIB rod fragments. We expressed the C-terminal 305-residue rod fragment of the myosin IIB heavy chain (BRF305) in MRC-5 SV1 TG1 cells. As a result, unstable morphology was observed like MHC-IIB(-/-) fibroblasts. This phenotype was not observed in cells expressing BRF305 mutants: 1) with a defect in assembling, 2) lacking N-terminal 57 residues (N-57), or 3) lacking C-terminal 63 residues (C-63). A myosin IIA rod fragment ARF296 corresponding to BRF305 was not effective. However, the chimeric ARF296, in which the N-57 and C-63 of BRF305 were substituted for the corresponding regions of ARF296, acquired the ability to induce unstable morphology. We propose that the N-57 and C-63 of BRF305 are involved in self-recognition when myosin IIB molecules assemble into homo-filament.
Sato
Masaaki K
MK
Division of Chemistry, Graduate School of Science, Hokkaido University, Sapporo, 060-0810 Japan.
Takahashi
Masayuki
M
Yazawa
Michio
M
D000199:Actins / Q000378:metabolism; D000595:Amino Acid Sequence; D048430:Cell Shape; D003599:Cytoskeleton / Q000378:metabolism; D005347:Fibroblasts / Q000166:cytology; D005799:Genes, Dominant; D049452:Green Fluorescent Proteins / Q000378:metabolism; D006801:Humans; D047468:Immunoprecipitation; D008969:Molecular Sequence Data; D015879:Myosin Subfragments / Q000737:chemistry; D024501:Nonmuscle Myosin Type IIB / Q000737:chemistry* / Q000172:deficiency / Q000378:metabolism*; D010641:Phenotype; D011485:Protein Binding; D020033:Protein Isoforms / Q000737:chemistry / Q000378:metabolism; D017384:Sequence Deletion; D013329:Structure-Activity Relationship
D000199:Actins; D015879:Myosin Subfragments; D020033:Protein Isoforms; D049452:Green Fluorescent Proteins; D024501:Nonmuscle Myosin Type IIB