Correction

BIOCHEMISTRY. For the article “Functional transitions in myosin: Formation of a critical salt-bridge and transmission of effect to the sensitive tryptophan” by Hirofumi Onishi, Shin-ichiro Kojima, Kazuo Katoh, Keigi Fujiwara, Hugo M. Martinez, and Manuel F. Morales, which appeared in number 12, June 9, 1998, of Proc. Natl. Acad. Sci. USA (95, 6653–6658), the authors note the following correction. Recently, it has been discovered that the heavy meromyosin (HMM) mutant described as E470R/R247E HMM was actually P548G HMM. Examination and subsequent experiments with authentic E470R/R247E HMM revealed that although its tryptophan fluorescence is increased upon addition of ADP or ATP, its intrinsic ATPase at all ATP concentrations examined, 0.5–4 mM, was far less than that of wild type. As before, it was not actin-activated. Therefore, our revised conclusions are: (i) our observations do not conflict with Rayment's suggestion that at some stage preceding hydrolysis, bridge formation occurs; (ii) for fluorescence enhancement, the reversed dipole of the mutant is at least partly effective; (iii) although ATP binds as suggested by the partial tryptophan enhancement, the salt bridge does not form properly, so hydrolysis is therefore precluded; and (iv) we cannot deduce anything about actin activation because intrinsic ATPase is absent. It seems that in E470R and R247E HMMs, electrical repulsion precludes bridge formation, and therefore, hydrolysis.