Myo3A, one of two class III myosin genes expressed in vertebrate retina, is localized to the calycal processes of rod and cone photoreceptors and is expressed in the sacculus.
The striped bass has two retina-expressed class III myosin genes, each composed of a kinase, motor, and tail domain. We report the cloning, sequence analysis, and expression patterns of the long (Myo3A) and short (Myo3B) class III myosins, as well as cellular localization and biochemical characterization of the long isoform, Myo3A. Myo3A (209 kDa) is expressed in the retina, brain, testis, and sacculus, and Myo3B (155 kDa) is expressed in the retina, intestine, and testis. The tails of these two isoforms contain two highly conserved domains, 3THDI and 3THDII. Whereas Myo3B has three IQ motifs, Myo3A has nine IQ motifs, four in its neck and five in its tail domain. Myo3A localizes to actin filament bundles of photoreceptors and is concentrated in the calycal processes. An anti-Myo3A antibody decorates the actin cytoskeleton of rod inner/outer segments, and this labeling is reduced by the presence of ATP. The ATP-sensitive actin association is a feature characteristic of myosin motors. The numerous IQ motifs may play a structural or signaling role in the Myo3A, and its localization to calycal processes indicates that this myosin mediates a local function at this site in vertebrate photoreceptors.
Dosé
Andréa C
AC
University of California, Berkeley 94720-3200, USA. acdose@socrates.berkeley.edu
Hillman
David W
DW
Wong
Cynthia
C
Sohlberg
Lorraine
L
Lin-Jones
Jennifer
J
Burnside
Beth
B
D000199:Actins / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D001492:Bass / Q000378:metabolism; D002147:Calmodulin / Q000378:metabolism; D003599:Cytoskeleton / Q000378:metabolism; D006801:Humans; D008969:Molecular Sequence Data; D018995:Myosin Heavy Chains / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D025102:Myosin Type III; D010802:Phylogeny; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism*; D012160:Retina / Q000737:chemistry / Q000166:cytology / Q000378:metabolism*; D017949:Retinal Cone Photoreceptor Cells / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure; D017948:Retinal Rod Photoreceptor Cells / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure; D012444:Saccule and Utricle / Q000737:chemistry / Q000378:metabolism*; D016415:Sequence Alignment; D014018:Tissue Distribution; D014404:Tubulin / Q000378:metabolism
D000199:Actins; D002147:Calmodulin; D020033:Protein Isoforms; D014404:Tubulin; D000255:Adenosine Triphosphate; C491724:MYO3A protein, human; D025102:Myosin Type III; D018995:Myosin Heavy Chains