THE SECONDARY STRUCTURE OF PHOSPHOLAMBAN - A 2-DIMENSIONAL NMR-STUDY

Phospholamban (PLN) is an intrinsic membrane protein of 52 amino acids which regulates the Ca2+ pump of the sarcoplasmic reticulum of heart, slow-twitch and smooth muscle (SR): it is normally assumed to exist i n the membrane as a homopentamer. A monomeric analogue of phospholamba n PLN(C41F), in which Cys(41) was replaced by a Phe,was synthesized an d its conformation studied by H-1 NMR spectroscopy in a 1:1 mixture of chloroform/methanol. Most of the resonances in the H-1 NMR spectra we re assigned. The work has shown that the C-terminal hydrophobic portio n forms a very stable alpha-helix. The hydrophilic N-terminal part ado pts an alpha-helix configuration which is much less stable except for the stretch containing the phosphorylation sites. (C) 1995 Academic Pr ess, Inc.