Mammary gland Ca2+-binding (-dependent) proteins: identification as calelectrins and calpactin I/p36.
Calcium-binding (-dependent) proteins (CBPs) associated with the spreading of mammary epithelial cell cultures have been identified as various calelectrins and calpactins (p36). In immunoblot analysis, the CBPs of 30-36 kD and 68-70 kD variously react with different calelectrin and calpactin I monomer/p36 antisera. The same immunoreactive proteins were shown to be present in virgin mammary glands and collagen gel mouse mammary epithelial cell cultures. The mammary CBPs show extensive immunochemical relatedness; however, they fail to show cross-reaction with antiserum to calpactin II (lipocortin) antiserum. These immunoreactive CBPs comigrate in electrophoresis with 35S-methionine-labeled CBPs isolated from mammary epithelial cell cultures. Unlike calmodulin, the mammary CBPs that correspond to calelectrins and calpactin I monomer/p36 are not stable to thermal denaturation. The mammary CBPs bind to epithelial cell membranes in a Ca2+-dependent manner and are differentially released from ruptured cells, compared with calmodulin, suggesting subcellular localization. Phenothiazine-agarose and phenylagarose are equivalent in their ability to bind the mammary CBPs. Thus, mammary gland CBPs of 30-36 kD and 68-70 kD have been shown to be related or equivalent to the calelectrins and to calpactin I monomer/p36. Since these proteins are known to bind Ca2+, we conclude that the mammary gland CBPs are also Ca2+-binding proteins. The mammary gland CBPs are immunologically related and probably represent members of a larger family of related proteins.
Hom
Y K
YK
Biology Board of Studies, University of California, Santa Cruz 95064.
Sudhof
T C
TC
Lozano
J J
JJ
Haindl
A H
AH
Rocha
V
V
D000818:Animals; D017302:Annexins; D002135:Calcium-Binding Proteins / Q000378:metabolism*; D002846:Chromatography, Affinity; D004591:Electrophoresis, Polyacrylamide Gel; D005260:Female; D006358:Hot Temperature; D007163:Immunosorbent Techniques; D008321:Mammary Glands, Animal / Q000378:metabolism*; D008566:Membranes / Q000378:metabolism; D051379:Mice; D008807:Mice, Inbred BALB C; D008970:Molecular Weight; D011489:Protein Denaturation
D017302:Annexins; D002135:Calcium-Binding Proteins