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. 1999 Dec 10;463(1-2):146-50.
doi: 10.1016/s0014-5793(99)01589-6.

Smooth muscle alpha-tropomyosin crosslinks to caldesmon, to actin and to myosin subfragment 1 on the muscle thin filament

N L Golitsina  1 , S S Lehrer
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Free article

Smooth muscle alpha-tropomyosin crosslinks to caldesmon, to actin and to myosin subfragment 1 on the muscle thin filament

N L Golitsina et al. FEBS Lett. .
Free article

Abstract

To obtain proximity information between tropomyosin (Tm) and caldesmon (CaD) on the muscle thin filament, we cloned gizzard alphaTm and created two single Cys mutants S56C/C190S (56Tm) and D100C/C190S (100Tm). They were labeled with benzophenone maleimide (BPM) and UV-irradiated on thin filaments. One chain of BPM-56Tm and two chains of BPM-100Tm crosslinked to CaD. Only BPM-100Tm crosslinked to actin in the absence and presence of CaD and binding of low ratios of myosin subfragment 1 (S1) prevented the crosslinking. Tm-S1 crosslinks were produced when actin.Tm was saturated with S1. Thus, CaD on the actin.Tm filament is located <10 A away from Tm amino acids 56 and 100; in the closed state of the actin.Tm filament, Tm residue 100 is located close to the actin surface and is moved further away in the S1-induced open state; in the open state, S1 binds close to Tm.

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