Studies on the properties of chemically modified actin. I. Photooxidation, succinylation, nitration

1. The biological properties of photooxidized, succinylated and nitrated Factin were studied. 2. After 2 min of illumination, when only 2 histidine residues disappeared, the α-actinin sensitivity was completely abolished, the polymerizability and myosin ATPase (ATP phosphohydrolase, EC 3.6.1.3) activation property greatly diminished, and superprecipitation and actomyosin formation slightly diminished. 3. All the studied biological activities but myosin ATPase activation disappeared, if 27% of the ε{lunate}-amino groups of actin were succinylated. 4. Tetranitromethane nitrates mostly the tyrosine residues and sulfhydryl groups of actin, tryptophan residues are affected only at high concentration of the reagent. Viscosity and actomyosin formation of actin sharply decreased, and ATPase activation slightly decreased in consequence of nitration, while there was no change in the superprecipitation property of the actomyosin reconstituted from nitrated actin.