| First Author | Mettikolla P | Year | 2009 |
| Journal | Biochemistry | Volume | 48 |
| Issue | 6 | Pages | 1264-71 |
| PubMed ID | 19159226 | Mgi Jnum | J:308168 |
| Mgi Id | MGI:6725897 | Doi | 10.1021/bi801629d |
| Citation | Mettikolla P, et al. (2009) Fluorescence lifetime of actin in the familial hypertrophic cardiomyopathy transgenic heart. Biochemistry 48(6):1264-71 |
| abstractText | Clinical studies have revealed that the D166V mutation in the ventricular myosin regulatory light chain (RLC) can cause a malignant phenotype of familial hypertrophic cardiomyopathy (FHC). It has been proposed that RLC induced FHC in the heart originates at the level of the myosin cross-bridge due to alterations in the rates of cross-bridge cycling. In this report, we examine whether the environment of an active cross-bridge in cardiac myofibrils from transgenic (Tg) mice is altered by the D166V mutation in RLC. The cross-bridge environment was monitored by tracking the fluorescence lifetime (tau) of Alexa488-phalloidin-labeled actin. The fluorescence lifetime is the average rate of decay of a fluorescent species from the excited state, which strongly depends on various environmental factors. We observed that the lifetime was high when cross-bridges were bound to actin and low when they were dissociated from it. The lifetime was measured every 50 ms from the center half of the I-band during 60 s of rigor, relaxation and contraction of muscle. We found no differences between lifetimes of Tg-WT and Tg-D166V muscle during rigor, relaxation and contraction. The duty ratio expressed as a fraction of time that cross-bridges spend attached to the thin filaments during isometric contraction was similar in Tg-WT and Tg-D166V muscles. Since independent measurements showed a large decrease in the cross-bridge turnover rate in Tg-D166V muscle compared to Tg-WT, the fact that the duty cycle remains constant suggests that the D166V mutation of RLC causes a decrease in the rate of cross-bridge attachment to actin. |
