| Affiliation: | (1) Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, D. F., Mexico;(2) Departamento de Bioquímica, Facultad de Medicina, Universidad Nacional Autónoma de México, D. F., Mexico;(3) Area Academica de Nutricion, Instituto de Ciencias de la Salud, Universidad Autonoma del Estado de Hidalgo, Pachuca, Hidalgo, Mexico;(4) Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Apartado Postal 70243, 04510 Mexico, D. F., Mexico |
| Abstract: | The F1-inhibitor protein complex (F1-IP) was purified from heart submitochondrial particles. Size exclusion chromatography of the endogenous complex showed that it contains dimers (D) and monomers (M) of F1-IP. Further chromatographic analysis showed that D and M interconvert. At high protein concentrations, the interconversion reaction is shifted toward the D species. The release of the inhibiting action of IP is faster at low than at high protein concentrations. During activation of F1, the M species accumulates through a process that is faster than the release of IP from F1. These findings indicate that the activation of F1-IP involves the transformation of D into M, which subsequently loses IP. The spectroscopic characteristics of D, M, and free F1 show that the binding of IP and dimerization modifies the fluorescence intensity of tyrosine residues and that of the single tryptophan of F1 which is far from the IP binding site. |
