Myosin isoforms

Some of the molecules responsible for hair-cell transduction have been identified. A few key molecules, some already described, have been identified as part of the transduction complex (Fig. 51-6). Myosin molecules clearly play essential roles, and hair cells express a variety of myosin isoforms. Because it is located at the tips of the stereocilia, near the tip-link anchors, myosin-1 c is the best candidate for the adaptation motor. Selective inhibition of a sensitized myosin- lc mutant with an ADP analog proved that this myosin participates in adaptation [14], although contribution by other myosins has yet to be ruled out. For example, mice with near-null mutations in myosin-7a have defects in auditory transduction that are consistent with alterations in the adaptation machinery, suggesting a central role for this myosin too [15]. 

All myosin Isoforms can Interact with actin filaments through their head domains, but their cellular roles differ, depending on their tall domains (see Table 19-3). 

The finding that the nonmuscle LC20 content in porcine carotid artery (16 3% of the total LC20) matches that of nonmuscle myosin HC content (14 2%) raised the question of a specific function of nonmuscle myosin isoforms (Gaylinn et al., 1989). On the other hand, the proportion of nonmuscle LC20 to... 

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Myosin isoform transitions and SMC phenotypes during development in rabbit aorta... 

Fig. 6. Myosin isoforms and SMC phenotypes during rabbit development, d.a., ductus arteriosus ao., aorta.

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Babij P, Kawamoto S, White S, Adelstein RS, Periasamy M (1992) Differential expression of SMI and SM2 myosin isoforms in cultured vascular smooth muscle. Am J Physiol 262 (Cell Physiol 31) C607-C613... 

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