Which conformation of the MM-CK molecule is responsible for a strong bond in the M-line of sarcomere?
Abstract
In the previous study we showed maximum of substrate channeling in moderate acid pH 6.95 and subsequently we found a strong pH dependence of CK bond in the M-line within the physiological range pH 6.8-7.2. It could be induced by conformational changes of the CK molecule.
In order to observe underlying conformational changes, we measured emission spectra of excited intrinsic tryptophan residues (Trp) within the pH range of 6.80-7.50. We did not obtain any dramatic differences in the emission spectra with respect to the pH changes.
In spite of this data hydrophobic fluorescent probe 1,8-ANS (1-anilinonaphthalene-8- sulfonic acid), which is used for partially mapping of unfolded states of proteins, showed slow but significant unfolding during increasing pH. The results of this study show that the strong bond of MM-CK in the M-line of myofibrils is evoked by more tight conformation of the CK molecule under acid pH.