Membrane proteins phospholamban

The uniquely high resolution structural data available for the SERCAIa Ca2+ pump illuminates the structure of all P-type transporters. Unlike the Na,K pump, the catalytic subunit of the SERCA Ca2+ pumps is active and does not require association with another subunit. However, the cardiac isoform, SERCA-2a, associates with a small membrane protein, phospholamban, that can... 

N.J. Traaseth, G. Veglia, Probing excited states and activation energy for the integral membrane protein phospholamban by NMR CPMG relaxation dispersion experiments, Biochim. Biophys. Acta 1798 (2010) 77—81. 

Phospholamban (PLB or PLN) is a single-pass, 52-residue integral membrane protein that regulates myocardial contractility by direct physical interaction with sarco(endo)plasmic reticulum Ca-ATPase (SERCA), a 110-kDa enzyme that maintains calcium homeostasis in the sarcoplasmic... 

Phospholamban is a homopentameric membrane protein involved in muscle contraction through regulation of the calcium pump in cardiac muscle cells. The stmcture of the unphospho-rylated protein solved in DPC micelles reveals a symmetric pentamer of phospholamban monomers (Fig. 2g) stabilized by leucine/isoleucine zipper motifs along the transmembrane domains (51). Notably, another stmcture was produced for phospholamban (Fig. 2h) that used a variant of the traditional simulated annealing and molecular dynamics protocol that reduced the chances of entrapment in local minima (52). 

Roosild TP, Greenwald J, Vega M, Castronovo S, Riek R, Choe S. NMR structure of Mistic, a membrane-integrating protein for membrane protein expression. Science 2005 307 1317-1321. Oxenoid K, Chou JJ. The structure of phospholamban pentamer reveals a channel-like architecture in membranes. Proc. Natl. Acad. Sci. U.S.A. 2005 102 10870-10875. 

Vorherr, T., Wrzosek, A., Chiesi, M., and Carafoli, E. (1993). Prot. Sci. 2, 339-347. Total synthesis and functional properties of the membrane-intrinsic protein phospholamban. 

Activity is modulated by other proteins present in the membrane. These include a glycoprotein (MW 53 000) which stimulates ATPase activity a 60 000 molecular weight protein, which is phosphorylated in a calmodulin-dependent fashion, affects accumulation of calcium while the activity of the enzyme is affected by an endogenous kinase and phosphatase which phosphorylates and dephosphorylates the protein. " Phospholamban is a proteolipid (MW 22 000) in cardiac SR which undergoes both cyclic AMP-dependent and calcium-calmodulin-dependent phosphorylation, but at different sites. All these proteins are probably involved in regulating the activity of the calcium pump. 

Zamoon J, Nitu F, Karim C, Thomas DD, Veglia G (2005) Mapping the interaction surface of a membrane protein unveiling the conformational switch of phospholamban in calcium pump regulation. Proc Natl Acad Sci USA 102 4747 752... 

Structural changes in the lipid bilayer upon insertion of the transmembrane domain of the membrane-bound protein phospholamban (PLB) were studied using P and solid state NMR. Phospholamban is a 52-amino acid integral membrane protein that regulates the flow of Ca " ions in cardiac muscle cells. Solid state NMR experiments were carried out to study the behavior of lipid bilayers in the presence of the hydrophobic PLB at different temperatures. P NMR was used to study the different phases formed by phospholipid membranes. Simulations of the P NMR spectra were carried out to reveal the formation of different vesicle sizes upon PLB insertion. Molecular order parameters were calculated by performing solid state NMR studies on deuterated phospholipid bilayers. 

Recent applications of solid state NMR to membrane protein characterisation also include the light-harvesting complex II of Rhodopseudomonas acidophila", glycinated mastoparan-X , diacylglyerol kinase from E. coli" phospholamban , Rv2433c from Mycobacterium tuberculosis and the ABC transporter LmrA from Lactococcus lactis". ... 

Phospholamban (PEN) is a single-pass 52-amino acid membrane protein that interacts with the Ca-ATPase (SERCA) in cardiac muscle. Wild-type PEN, existing as a pentamer, takes the pinwheel topology as the predominant conformation with the cytoplasmic domain interacting with the membrane surface [262—264]. The PEN monomer (AFA-PEN), in which three TM cysteines are replaced by A36, F41 and A46, is functionally active and in equilibrium between ordered (T) and disordered (R) states [265,266] N backbone and Ile-methyl dispersion data indicate that residues within domain la (residues 1-16), the loop (17-22), and domain lb (23-30) of PEN undergo is-ms dynamics (feex=6100 800 s at 17 °C) [267]. 

Researchers have studied whether acyl-chain order could be responsible for the preferred sterol interaction with SMs. Acyl-chain order was deduced from diphenylhexatriene anisotropy and from the deuterium order parameter obtained by H-NMR on bilayers made from either 14 0/14 0(d27)-PC, or 14 0(d27)-SM7 Some researcher analyzed the ground and excited states of phospholamban (PLN), a membrane protein that regulates sarcoplasmic reticulum (SR) calcium ATPase (SERCA), in dilferent membrane mimetic environments. Gustavsson et al. have previously proposed that the conformational equilibrium of PLN are central to SERCA regulation. They have now shown that these equilibrium detected in micelles and bicelles are also present in native sarcoplasmic reticulum lipid membranes as probed by MAS solid-state NMR. ... 

Using model proteins Walsh and Wang have discussed in detail the utilization of dipolar waves to extract structural information such as the periodicity of peptide plane, its planarity, kink or curvature of a-helix and irregularities of P-strand. Veglia and co-workers have exploited the amplitude and average values of dipolar waves in determination of helical membrane protein topology. In the latter studies N-labelled phospholamban protein was used as a test molecule. 

Phospholamban (PLB) is a membrane protein that regulates heart musele relaxation rates via interaetions with sareoplasmic reticulum Ca ATPase (SERCA). When PLB is phosphorylated or mutated (R9C-PLB), inhibition of SERCA is relieved. C and SS NMR spectroscopy was utilized to investigate eonformational ehanges of PLB upon phosphorylation and R9C mutation. C 0 NMR speetra of the cytoplasmic domain revealed 2 a-helieal struetural eomponents with population ehanges upon phosphorylation and R9C mutation. The N NMR spectra indicated an inerease in baekbone dynamics of the cytoplasmic domain. Wild-type PLB (WT-PLB), Ser-16-phosphotylated PLB (P-PLB), and R9C-PLB all had a veiy dynamic domain Ib, and the transmembrane domain had an immobile eomponent The N NMR spectra indicated that the cytoplasmic domain of R9C-PLB adopted an orientation similar to P-PLB and shifted away from the membrane surface. Domain Ib (Leu-28) of P-PLB and R9C-PLB lost the alignment. R9C-PLB adopted a conformation similar to P-PLB with a population shift to a more extended and disordered state. ... 

Increased cAMP in smooth musle cells causes muscle relaxation through activation of cAMP-dependent PK (PKA). PKA phosphorylates MLGK and phospho-MLCK (P-MLGK) is poorly activated by Ca2+-CaM. PKA also phosphorylates an ER protein called phospholamban, the P-phospholamban entity increasing the activity of the ER membrane Ca2+-ATPase which lowers cytosolic Ca2+ concentration and thus prevents smooth muscle contraction. 

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