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Toshiaki HIRATSUKA, Koki UCHIDA, Selective Release of Light Chain-2 from Pig Cardiac Myosin by Chemical Modification of Specific Lysyl Residues with N-Methyl-2-Anilinonaphthalene-6-Sulfonyl Chloride, The Journal of Biochemistry, Volume 82, Issue 4, October 1977, Pages 983–990, https://doi.org/10.1093/oxfordjournals.jbchem.a131803
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Abstract
Two moles of lysyl residues on cardiac myosin from the left ventricle of pig heart rapidly reacted with N-methyl-2-anilinonaphthalene-6-sulfonyl chloride (Mns-Cl).
Introduction of Mns groups into myosin caused the selective release of light chain-2 (LC2). The amount of LC2 released increased with increase in the number of Mns groups introduced and reached a constant level, 45% of total LC2 content, essentially without affecting myosin ATFase activities. Divalent metal ions and Mg2+-ATP partially protected myosin against labeling with Mns-C1 and the resulting release of LC2, while EDTA had opposite effects.
Treatments with l-dimethylaminonaphthalene-5-sulfonyl chloride (Dns-Cl) and 2, 4, 6- trinitrobenzene sulfonate (TNBS) also caused the release of LC2, but these treatments were accompanied by the release of light chain-1 (LC1), irreversible aggregation of myosin and loss of ATPase activity.
Concomitant labeling of the released LC2 with Mns-Cl occurred in proportion to the extent of labeling of myosin. However, there was no relation between the amount of LC2 released and the extent of labeling of LC2 itself. Mns and Dns groups introduced into the myosin molecule were visualized on sodium dodecyl sulfate-polyacrylamide gels by using a UV lamp. Even after separation of the released LC2, fluorescence was still located on a band corresponding to the remaining LC2.
It is suggested that the selective release of LC2 from pig cardiac myosin by Mns-Cl is not caused by labeling of LC2 itself but by the labeling of a certain region on HC, where the essential lysyl residues function as a trigger for the release of LC2.
