Peripheral membrane proteins of sarcoplasmic and endoplasmic reticulum. Comparison of carboxyl-terminal amino acid sequences.
Peripheral endoplasmic reticulum membrane proteins residing in the lumen of the endoplasmic reticulum occupy the same space as other secreted proteins. The presence of a four amino acid salvage or retention signal (KDEL-COOH = Lys-Asp-Glu-Leu-COOH) at the carboxyl-terminal end of peripheral membrane proteins has been shown to represent a signal or an essential part of a signal for their retention within the endoplasmic reticulum membrane. In heart and skeletal muscle, a number of sarcoplasmic reticulum proteins have recently been identified which are peripheral membrane proteins. The high-affinity calcium-binding protein (55 kilodaltons (kDa] appears to conform to the above described mechanisms and contains the KDEL carboxyl-terminal tetrapeptide. Thyroid hormone binding protein is present in the sarcoplasmic reticulum, in addition to its endoplasmic reticulum location, and has a modified but related tetrapeptide sequence (RDEL = Arg-Asp-Glu-Leu), which also probably functions as the retention signal. Calsequestrin and a 53-kDa glycoprotein, two other peripheral membrane proteins residing in the lumen of the sarcoplasmic reticulum, do not contain the KDEL retention signal. The sarcoplasmic reticulum may have developed a unique retention mechanism(s) for these muscle-specific proteins.
Fliegel
L
L
Department of Pediatrics, University of Alberta, Edmonton, Canada.
Burns
K
K
Wlasichuk
K
K
Michalak
M
M
D000595:Amino Acid Sequence; D000818:Animals; D004721:Endoplasmic Reticulum / Q000032:analysis*; D006801:Humans; D008565:Membrane Proteins; D008969:Molecular Sequence Data; D012519:Sarcoplasmic Reticulum / Q000032:analysis*
D008565:Membrane Proteins