2101 



Cooley, L. B. 1978. 



Evidence for the phosphorylation of paramyosin. Biophys . J. 21(3), 

 Muscle proteins IV: 141a (abstract TU-POS-F11) . 



Paramyosin isolated from Meraenaria meraenaria appears to contain bound 

 inorganic phosphate which is involved in intermolecular interactions. 

 Three to four phosphates per molecule have been found in native paramyosin. 

 Dialyzing paramyosin against 0.01N KOH at 4°C for 24 hrs appears to remove 

 one or more phosphates. Partial dephosphorylation may explain the change 

 in solubility of alkali-treated paramyosin and the slight change in the 

 near ultraviolet circular dichroism of alkali treated paramyosin. In ad- 

 dition, partial dephosphorylation may occur during the titrations of para- 

 myosin, explaining why the forward and reverse titrations at high ionic 

 strength are not the same. No change in molecular weight, length, or per- 

 cent a-helicity was found in alkali treated paramyosin. - modified author's 

 abstract - J.L.M. 



2102 



Cooley, L. B./and S. Krause. 1979. 



The unusual minimum in solubility of paramyosin as the ionic strength is 

 varied at pH 7.00. Biophys. J. 25(2), Part 2, Muscle proteins: 246a 

 (abstract T-PM-Po82) . 



Native and partially degraded paramyosin from Meraenaria meraenaria exhib- 

 ited a solubility minimum at pH 7.00 in the ionic strength range 0.05M to 

 0.07M. At higher and at lower ionic strengths the solubility increased. 

 This is in sharp contrast to the behavior exhibited by most proteins. In 

 general, a protein is insoluble in distilled water and its solubility in- 

 creases as the ionic strength increases until a maximum in solubility is 

 reached. At higher ionic strengths the protein is salted out. Alkali 

 treatment which resulted in partial dephosphorylation of paramyosin affected 

 the solubility at ionic strengths above 0.05 M, but not at lower ionic 

 strengths. An explanation is suggested based on charge interactions be- 

 tween paramyosin molecules. The model is supported by the results of pH 

 titrations at ionic strengths below and above the ionic strength of the 

 solubility minimum. - modifed from abstract - J.L.M. 



2103 



Cooley, Linda B., William H. Johnson, and Sonja Krause. 1979. 



Phosphorylation of paramyosin and its possible role in the catch 

 mechanism. J. Biol. Chem. 254(7): 2195-2198. 



Recent developments indicate that paramyosin may be located on the surface 

 of thick filaments and that some thick filaments are surrounded by other 

 thick filaments instead of by thin filaments. Paramyosin molecules on one 

 thick filament may be able to interact with paramyosin molecules on other 

 thick filaments, locking the muscle in the contracted state. It has been 

 shown that solutions of a-R-paramyosin will form paracrystals which are 

 essentially side by side aggregates of smaller paracrystals. The solu- 

 bility of paramyosin and therefore certain paramyosin-paramyosin inter- 

 actions are affected by the extent of phosphorylation of paramyosin. Thus, 

 the phosphorylation of paramyosin may be. involved in paramyosin aggrega- 

 tion in vivo and therefore in the catch mechanism. An increase in the 

 degree of phosphorylation could result in an increase in the aggregation 

 between paramyosin molecules and an increase in interactions between para- 

 myosin contained in adjacent thick filaments and, therefore, in passive 

 tension maintenance. Dephosphorylation could result in a decrease in 

 interactions between filaments, and therefore in muscle relaxation. - from 

 authors' discussion. - J.L.M. 



584 



