Phospholamban bioactive peptide and similar proteins
Vertebrate phospholamban (PLN) belongs to a family of bioactive peptides which includes vertebrate sarcolipin (SLN), and the invertebrate sarcolamban (SCLA, and SCLB). SCLA and SCLB are encoded within a single putative noncoding transcript, pncr003:2L; PLN and SLN are each encoded within a single exon of a spliced transcript. PLN is chiefly expressed in the cardiac muscle, while SLN is expressed in the atria of the heart and embryonic slow-type skeletal muscle; SCL is found in cardiac and somatic muscle of Drosophila melanogaster. PLN and SLN are each a single-pass transmembrane alpha-helix that interacts directly with the sarcoplasmic reticulum (SR) calcium pump (SERCA), lower its affinity for Ca2+, thereby decreasing the rate of Ca2+ reuptake into the SR from the sarcoplasm. In the heart, PLN and SLN inhibit the activity of SERCA2a isoform and function as important regulators of cardiac contractibility and disease. SCLA and SCLB are each predicted to form a single-pass transmembrane helix, localize to the SR with the SR calcium pump (Ca-P60A), and dampen its activity. PLN and SLN differ in their interaction with SERCA; PLN is an affinity modulator of SERCA. It is thought to form a pentamer in the membrane.
Comment:in this pinwheel topology one monomer is contacting 3 other monomers in the pentamer; the pentameric pore is too narrow to fit a fully hydrated ion;
Structure:1ZLL: human phospholamban in a bellflower-like assembly, pentamer interface; contacts at 4A
Comment:in the bellflower-like assembly the monomer contacts 2 other monomers in the pentamer, and forms a pentameric pore which could allow passage of small ions
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