ISSN:
1573-4919
Keywords:
cAMP-dependent protein kinase
;
autophosphorylation
;
limited proteolysis
;
isoforms of regulatory subunits
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Chemistry and Pharmacology
,
Medicine
Notes:
Abstract Two forms of the regulatory subunit of the type II cAMP-dependent protein kinase (RII55 and RII52) were identified from bovine heart by gel electrophoretic behaviour. After autophosphorylation the RII55 isoform migrated more slowly (RII55/57) while the migration of RII52 isoform did not shift. Both isoforms showed different affinity for cAMP. The RII55/57 isoform was eluted from a cAMP-agarose column at 10 mM cAMP at low ionic strenght whereas the RII52 isoform required cAMP, plus 2 M NaCl. Partial proteolysis, using trypsin or formic acid, of autophosphorylated regulatory subunit isoforms resulted in different cleavage pattern as determined by peptide mapping. However, the V8125I-peptides patterns of both isoforms are quite similar. Incubation of partially purified holoenzyme with 10 nM [γ-32P]ATP (low ATP concentration) yielded a single band of Mr = 57,000 which corresponds to the RII55/57 isoform. The incubation, however, at 20 µM [γ-32P]ATP yielded two phosphobands corresponding to both RII55/57 and RII52 isoforms. The phosphorylation of RII52 took place with a lower efficiency and was more sensitive to the cAMP than the corresponding phosphorylation of the RII55/57.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00228450
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