Why labelling the ‘fast-reacting thiols’ of myosin reduces force output: re-assessing a year at the University of California San Francisco (1987-8)

Figures

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  Fig. 1. Testing the effect of IATR labelling on force generation. A Single glycerinated rabbit psoas fibres, labelled with IATR generated force when the solution was changed from relaxing to activating solution. IATR labelling was confirmed by SDS PAGE of the samples after this analysis and using fluorescence to identify that it was predominantly the myosin heavy chain (MHC) that was labelled. B Results from at least 3 separate experiments to test the effect of lATR labelling on the relative force output. Mean ± S.D. is shown for each of the values. Curve fitted using Prizm (GraphPad)

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  Fig. 2. A Sequence alignment of β-cardiac myosin heavy chain (β—MHC), smooth muscle myosin (SMM), non-muscle myosin 2 A (NM2A) and myosin 5a (Myo5a) to show the positions of the highly reactive thiol in the SH1 helix (substituted to serine in Myo5a), together with a second cysteine residue, termed SH2, which can also be labelled, although the SH1 thiol is most reactive. B The SH1 thiol (C/S693) lies between the relax helix and the SH1 helix and labelling of this residue with IATR would likely block the power stroke, as would labelling of the SH2 thiol (C684)

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  Fig. 3. Anthony Baker (LHS) and Roger Cooke (RHS) enjoying themselves at Michelle’s leaving party in San Francisco in 1988