Oligomerization is an intrinsic property of calsequestrin in normal and transformed skeletal muscle.
In skeletal muscle fibers, the high-capacity medium-affinity Ca(2+)-binding protein calsequestrin functions as the major Ca(2+)-reservoir of the sarcoplasmic reticulum. To determine the oligomeric status of calsequestrin, immunoblotting of microsomal proteins following chemical crosslinking was performed. Diagonal non-reducing/reducing two-dimensional gel electrophoresis was employed to unequivocally differentiate between cross-linked species of 63 kDa calsequestrin and calsequestrin-like proteins of higher relative molecular mass. Since chronic low-frequency stimulation has a profound effect on the expression of many muscle-specific protein isoforms, we investigated normal and conditioned muscle fibers. Calsequestrin was found to exist in a wide range of high-molecular-mass clusters in normal and chronically stimulated skeletal muscle fibers. Hence, oligomerization is an intrinsic property of this important Ca(2+)-binding protein and does not appear to be influenced by the fast-to-slow transformation process. Although fiber-type specific differences exist in the physiology of the skeletal muscle Ca(2+)-regulatory system, oligomerization of calsequestrin seems to be essential for proper functioning.
Maguire
P B
PB
Department of Pharmacology, University College Dublin, Ireland.
Briggs
F N
FN
Lennon
N J
NJ
Ohlendieck
K
K
D000818:Animals; D002135:Calcium-Binding Proteins / Q000737:chemistry / Q000378:metabolism; D002155:Calsequestrin / Q000737:chemistry*; D003432:Cross-Linking Reagents / Q000378:metabolism; D004285:Dogs; D004558:Electric Stimulation; D015180:Electrophoresis, Gel, Two-Dimensional; D008861:Microsomes / Q000737:chemistry; D008970:Molecular Weight; D018485:Muscle Fibers, Skeletal / Q000737:chemistry* / Q000502:physiology; D018482:Muscle, Skeletal / Q000737:chemistry* / Q000502:physiology; D011233:Precipitin Tests; D011487:Protein Conformation; D011817:Rabbits; D012519:Sarcoplasmic Reticulum / Q000737:chemistry; D013388:Succinimides / Q000378:metabolism
D002135:Calcium-Binding Proteins; D002155:Calsequestrin; D003432:Cross-Linking Reagents; D013388:Succinimides; C011240:dithiobis(succinimidylpropionate)