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

FEBS Letters

Golitsina, Nina L.¹  Lehrer, Sherwin S.¹ 

[1] Muscle Research Group, Boston Biomedical Research Institute, Boston, MA 02114, USA

关键词: Muscle thin filament;    Smooth muscle tropomyosin Cys mutant;    Caldesmon;    Actin;    UV crosslinking;    CaD;    caldesmon;    Tm;    tropomyosin;    56Tm and 100Tm;    Tm double mutant C190S/S56C and C190S/D100C;    respectively;    S1;    myosin subfragment 1;    NEM-S1;    N-ethylmaleimide treated S1;    BPM;    benzophenone-4-maleimide;    BPM-Tm;    BPM labeled Tm;   

DOI  :  10.1016/S0014-5793(99)01589-6

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

To obtain proximity information between tropomyosin (Tm) and caldesmon (CaD) on the muscle thin filament, we cloned gizzard αTm 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 Å 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.

【 授权许可】

Unknown