A novel mammalian myosin I from rat with an SH3 domain localizes to Con A-inducible, F-actin-rich structures at cell-cell contacts.
In an effort to determine diversity and function of mammalian myosin I molecules, we report here the cloning and characterization of myr 3 (third unconventional myosin from rat), a novel mammalian myosin I from rat tissues that is related to myosin I molecules from protozoa. Like the protozoan myosin I molecules, myr 3 consists of a myosin head domain, a single light chain binding motif, and a tail region that includes a COOH-terminal SH3 domain. However, myr 3 lacks the regulatory phosphorylation site present in the head domain of protozoan myosin I molecules. Evidence was obtained that the COOH terminus of the tail domain is involved in regulating F-actin binding activity of the NH2-terminal head domain. The light chain of myr 3 was identified as the Ca(2+)-binding protein calmodulin. Northern blot and immunoblot analyses revealed that myr 3 is expressed in many tissues and cell lines. Immunofluorescence studies with anti-myr 3 antibodies in NRK cells demonstrated that myr 3 is localized in the cytoplasm and in elongated structures at regions of cell-cell contact. These elongated structures contained F-actin and alpha-actinin but were devoid of vinculin. Incubation of NRK cells with Con A stimulated the formation of myr 3-containing structures along cell-cell contacts. These results suggest for myr 3 a function mediated by cell-cell contact.
Stöffler
H E
HE
Friedrich-Miescher-Laboratorium, Max-Planck-Gesellschaft, Tübingen, Germany.
Ruppert
C
C
Reinhard
J
J
Bähler
M
M
D000199:Actins / Q000302:isolation & purification*; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002147:Calmodulin / Q000032:analysis; D002451:Cell Compartmentation; D002460:Cell Line; D003208:Concanavalin A / Q000494:pharmacology; D004252:DNA Mutational Analysis; D018076:DNA, Complementary / Q000235:genetics; D005455:Fluorescent Antibody Technique; D007365:Intercellular Junctions / Q000737:chemistry*; D008565:Membrane Proteins / Q000235:genetics / Q000302:isolation & purification* / Q000378:metabolism; D008969:Molecular Sequence Data; D024461:Myosin Type I; D009218:Myosins / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification* / Q000378:metabolism; D015800:Protozoan Proteins / Q000235:genetics; D051381:Rats; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D012995:Solubility; D013329:Structure-Activity Relationship; D014018:Tissue Distribution
D000199:Actins; D002147:Calmodulin; D018076:DNA, Complementary; D008565:Membrane Proteins; C503808:Myo1e protein, rat; D015800:Protozoan Proteins; D003208:Concanavalin A; D024461:Myosin Type I; D009218:Myosins