Assuntos
Proteínas Musculares/isolamento & purificação , Adenosina Trifosfatases/metabolismo , Animais , Sítios de Ligação , Cálcio , Cromatografia de Afinidade , Cromatografia DEAE-Celulose , Cromatografia em Papel , Brometo de Cianogênio , Eletroforese em Gel de Poliacrilamida , Magnésio/farmacologia , Proteínas Musculares/metabolismo , Músculo Liso/análise , Músculos/análise , Músculos/enzimologia , Miocárdio/análise , Especificidade de Órgãos , Ligação Proteica , Coelhos , Espectrofotometria Ultravioleta , TemperaturaRESUMO
1. A series of defined peptides which span the complete sequence were produced from troponin I isolated from white skeletal muscle of the rabbit. 2. Two peptides, CF1 (residues 64-133) and CN4 (residues 96-117) inhibited the Mg2+-stimulated adenosine triphosphatase of desensitized actomyosin. This inhibition was potentiated by tropomyosin and the Mg2+-stimulated adenosine triphosphatase of desensitized actomyosin. This inhibition, unlike that of troponin I and peptides derived from it, was not potentiated by tropomyosin. 4. The most active inhibitor, peptide CN4, was 45-75% as effective as troponin I when compared on a molar basis. The inhibitory peptide, CN4, and also whole troponin I were shown by affinity chromatography to interact specifically with actin. 5. A strong interaction with troponin C was demonstrated with peptide CF2 (residues 1-47), from the N-terminal region of troponin I. Somewhat weaker interactions were shown with peptides CN5 (residues 1-21) and with the inhibitory peptide CN4. 6. The significance of these interactions for the mechanisms of action of troponin I is discussed.