The nonessential nature of sulfhydryl groups for ATPase activity in myosin. A cyanylation study.

Consequences of reacting the thiols of myosin subfragment 1

“…In this respect we confirm the results of Gaetjens et al (1964). Wiedner et al (1978) reported a monotonic increase under similar conditions. Also, we found the other ATPases to be decreasing more precipitously at high exposures, whereas (•) actin-activated Mg2+-ATPase; (O) Mg2+-ATPase.…”

“…However, the strategy of trying to eliminate direct thiol involvement, by asking whether the myosin functions persist after thiol reaction, was pioneered by Bárány and his associates (Gaetjens et al, 1964). Also, as this paper was readied for publication, there appeared a very interesting and closely related effort by Eckstein and his associates (Wiedner et al, 1978). We believe that the qualitative similarities in the conclusions of these two groups with our own are more important than the substantial quantitative differences among the three.…”

Reaction of 5,5'-dithiobis(2-nitrobenzoic acid) with myosin subfragment one: evidence for formation of a single protein disulfide with trapping of metal nucleotide at the active site

“…In fact, the observation that these thiols can be cross-linked with trapping of MgADP at the active site means they are unlikely to be involved in either binding or hydrolysis of the substrate. This agrees with the recent work of Wiedner et al (1978), who found that complete modification of the thiols of myosin with small blocking groups did not destroy enzyme activity.…”

Flexibility of the myosin heavy chain: direct evidence that the region containing SH1 and SH2 can move 10 .ANG. under the influence of nucleotide binding

“…The sequence given is from Elzinga and Collins (1977) and corresponds to residues 696-709 in the heavy chain sequence (M. Elzinga, personal communication). (Weidner et al, 1978) suggested that many of the thiols of myosin are structurally close to each other and could be involved in the disulfide formation observed.…”

“…The former suggestion, based on early chemical modification studies [Sekine & Kielley, 1964; reviewed by Reisler (1982)], has been ruled out by a variety of subsequent studies. For example, the blocking of SH, and SH2 by smaller reagents (Weidner et al, 1978;Botts et al, 1979) does not prevent ATP cleavage.…”