SERCA-Type of Calcium Pumps and Phospholamban

Re: Presentation 0237

Guoxiang Chu

On Mon Dec 14, Paul J. Bauer wrote
>The hypothesis that PLB is most effective as a pentamer is interesting. However, even so PLB runs in SDS-PAGE as pentamer,  can you really exclude that the physiologically active PLB is some fraction of monomeric PLB which co-exists in thermodynamic equilibrium with the pentameric aggregates?

Dear Dr. Bauer:

We agree that monomeric PLB is also active in inhibiting the SERCA2 affinity.  However, based on our transgenic mouse studies, the pentameric form appears to be more "functionally active" than monomeric PLB.  An inherent problem in all these studies is the use of SDS-PAGE to assign a molecular weight for the wild-type/mutant PLB and this may not reflect the in vivo state of the protein in native SR membranes.

Litsa Kranias

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