Conformational changes in myocardial actin in heart failure caused by toxic allergic myocarditis

The fluorescence resonance energy transfer method was used to study myocardial actin in rabbits with severe heart failure caused by toxic allergic myocarditis. It caused changes in orientation and microenvironment and increased excitation lifetime of fluorophores at the labels to Cys374 and Cys10 (subdomain 1), as well as at Lys61 and Tyr69 (subdomain 2). In addition, it increased the distance between Cys374 and Lys61, Cys10, and Tyr69, as well as between Tyr69 and Cys10. This attests to enlargement of the outer actin domain and more exposed and open arrangement of the tertiary structures of the N- and C-terminal regions and subdomain 2, accompanied by reduced conformational mobility. The relationships between actin conformation changes and decrease in contractile force and rate, as well as efficiency of actomyosin contraction are revealed, which agrees with the hypothesis on the leading role of actin in disturbances of contractile activity and energy transduction in the system of contractile proteins in heart failure. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 127, No. 4, pp. 395–399, April, 1999