SRP-27 is a novel component of the supramolecular signalling complex involved in skeletal muscle excitation-contraction coupling.
SRP-27 (sarcoplasmic reticulum protein of 27 kDa) is a newly identified integral membrane protein constituent of the skeletal muscle SR (sarcoplasmic reticulum). We identified its primary structure from cDNA clones isolated from a mouse skeletal muscle cDNA library. ESTs (expressed sequence tags) of SRP-27 were found mainly in cDNA libraries from excitable tissues of mouse. Western blot analysis confirmed the expression of SRP-27 in skeletal muscle and, to a lower extent, in heart and brain. Mild trypsin proteolysis combined with primary-structure prediction analysis suggested that SRP-27 has four transmembrane-spanning alpha helices and its C-terminal domain faces the cytoplasmic side of the endo(sarco)plasmic reticulum. The expression of SRP-27 is higher in fast twitch skeletal muscles compared to slow twitch muscles and peaks during the first month of post-natal development. High-resolution immunohistochemistry and Western blot analysis of subcellular fractions indicated that SRP-27 is distributed in both longitudinal tubules and terminal cisternae of the SR, as well as in the perinuclear membrane systems and the nuclear envelope of myotubes and adult fibres. SRP-27 co-sediments with the RyR (ryanodine receptor) macromolecular complex in high-salt sucrose-gradient centrifugation, and is pulled-down by anti-RyR as well as by maurocalcin, a well characterized RyR modulator. Our results indicate that SRP-27 is part of a SR supramolecular complex, suggesting the involvement of SRP-27 in the structural organization or function of the molecular machinery underlying excitation-contraction coupling.
Department of Experimental and Diagnostic Medicine, General Pathology section, University of Ferrara, Via Borsari 46, 44100 Ferrara, Italy.
Christophe
C
Bleunven
Susan
S
Treves
Xia
X
Jinyu
Elisa
E
Leo
Michel
M
Ronjat
Michel
M
De Waard
Georg
G
Kern
Bernhard E
BE
Flucher
Francesco
F
Zorzato
D000595:Amino Acid Sequence; D000818:Animals; D002460:Cell Line; D002522:Chlorocebus aethiops; D003001:Cloning, Molecular; D017124:Conserved Sequence; D018076:DNA, Complementary / Q000235:genetics; D004721:Endoplasmic Reticulum / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D006801:Humans; D008565:Membrane Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008969:Molecular Sequence Data; D009119:Muscle Contraction; D009124:Muscle Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D018482:Muscle, Skeletal / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D019837:Ryanodine Receptor Calcium Release Channel / Q000378:metabolism; D016415:Sequence Alignment; D015398:Signal Transduction
D018076:DNA, Complementary; D008565:Membrane Proteins; D009124:Muscle Proteins; D019837:Ryanodine Receptor Calcium Release Channel; C528172:Tmem38a protein, rat