Location of an essential carboxyl group along the heavy chain of cardiac and skeletal myosin subfragments 1

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Abstract
Cardiac [dog] and skeletal [rabbit] myosin subfragments 1 cleaved into 3 fragments were modified by 1-cyclohexyl-3-(2-morpholinoethyl)carbodiimide metho-p-toluenesulfonate in the presence of the nucleophile nitrotyrosine ethyl ester. The effects observed (1st-order kinetics of ATPase inactivation, incorporation of 1 mol of nitrotyrosine/mol of subfragment 1) were similar to those previously observed for the nondigested subfragments 1. For both native and digested subfragments 1, which were inactivated to the extent of .apprx. 70%, the location of the label nitrotyrosine was performed by immunological blotting with 125I-labeled anti-nitrotyrosine Ig. The modified residue was essentially located on the H chain for the native subfragments 1 and on the 50K peptide for the digested subfragments 1.