J. Biol. Chem., Vol. 263, Issue 19, 9142-9148, Jul, 1988
Purification and characterization of C1, the catalytic subunit of Saccharomyces cerevisiae cAMP-dependent protein kinase encoded by TPK1
MJ Zoller, J Kuret, S Cameron, L Levin and KE Johnson
Cold Spring Harbor Laboratory, New York 11724.
In the yeast Saccharomyces cerevisiae, three genes TPK1, TPK2, and TPK3
encode catalytic subunits of cAMP-dependent protein kinase. We have
purified and characterized the catalytic subunit, C1, encoded by the TPK1
gene. In order to purify C1 completely free of C2 and C3, a strain was
constructed that contained only the TPK1 gene and genetic disruptions of
the other two TPK genes. The cellular level of C1 was increased by
expressing the genes for C1 (TPK1) and yeast regulatory subunit (BCY1) on
multiple copy plasmids within this strain. Purification was accomplished by
a two-column procedure in which holoenzyme was chromatographed on
Sephacryl-200, then bound to an anti- regulatory subunit immunoaffinity
column. Pure C1 was released from the antibody column by addition of cAMP.
The protein migrated on a sodium dodecyl sulfate-polyacrylamide gel with an
Mr of 52,000. Kinetic analysis showed that the apparent Km for ATP and
Leu-Arg-Arg-Ala-Ser- Leu-Gly was 33 and 101 microM, respectively. The kcat
was determined to be 640 min-1. The protein weakly autophosphorylated,
incorporating less than 0.1 mol of phosphate/mol of catalytic subunit.
NH2-terminal sequencing revealed that the protein was blocked.