Identification of a cryptic protein kinase CK2 phosphorylation site in human complement protease C1r, and its use to probe intramolecular interaction
Abstract
Treatment of human C 1 r by CK2 resulted in the incorporation of [ 32P]phosphate into the N-terminal α region of its non-catalytic A chain. Fragmentation of 32P-labelled C 1 r followed by N-terminal sequence and mass spectrometry analyses allowed identification of Ser 189 as the phosphorylation site. Accessibility of Ser 189 was low in intact C1r, due in part to the presence of one of the oligosaccharides borne by the α region, further reduced in the presence of calcium, and abolished when C1r was incorporated into the C1s-C1r-C1r-C1s treatment or the C1 complex. In contrast, phosphorylation was enhanced in the isolated α fragment and insensitive to calcium. Taken together, these data provide support for the occurrence of a Ca 2+-dependent interaction between the α region and the remainder of the C1r molecule.
- Publication:
-
FEBS Letters
- Pub Date:
- January 1996
- DOI:
- 10.1016/0014-5793(96)00403-6
- Bibcode:
- 1996FEBSL.386...15P
- Keywords:
-
- Complement;
- C1r;
- Protein phosphorylation;
- Protein kinase CK2;
- Activated complement components are indicated by an overbar;
- e.g. C 1 r;
- CaMK-II;
- calcium/calmodulin-dependent kinase II;
- CK2;
- protein kinase CK2;
- DFP;
- diisopropyl phosphorofluoridate;
- PNGase-F;
- peptide N-glycosidase F;
- pNpGB;
- p-nitrophenyl-p‧-guanidinobenzoate;
- SDS-PAGE;
- sodium dodecyl sulfate-polyacrylamide gel electrophoresis