Rapid identification of NH2-terminal myristyl peptides by reversed-phase high-performance liquid chromatography

The protein kinase A catalytic subunit Cbeta2: molecular characterization and distribution of the splice variant

Cbeta2, a 46 kDa splice variant of the Cbeta isoform, is the largest isoform so far described for catalytic subunits from cAMP-dependent protein kinase in mammals. It differs from Cbeta in the first 15 N-terminal residues which are replaced with a 62-residue domain with no similarity to other known proteins. The Cbeta2 protein was identified in cardiac tissue by MS, microsequencing and C-subunit-isoform-selective antibodies. The Cbeta2 protein has a very low abundance of about 2% of total affinity-purified C subunits from bovine cardiac tissue. This, and the similarity of its biochemical properties to Calpha and Cbeta, are probably some of the reasons why the Cbeta2 protein has escaped detection so far. The abundance of the Cbeta2 protein differs dramatically between tissues, with most protein detected in heart, liver and spleen, and the lowest level in testis. Cbeta2 protein shows kinase activity against synthetic substrates, and is inhibited by the protein kinase inhibitor peptide PKI(5-24). The degree of Cbeta2 removal from tissue extracts by binding to PKI(5-24) depends on the cAMP level, i.e. on the dissociation state of the holoenzyme. Two sites in the protein are phosphorylated: Thr-244 in the activation segment and Ser-385 close to the C-terminus. By affinity purification and immunodetection Cbeta2 was found in cattle, pig, rat, mouse and turkey tissue and in HeLa cells. In the cAMP-insensitive CHO 10260 cell line, which has normal Cbeta but is depleted of Calpha, stable transfection with Cbeta2 restored most of the cAMP-induced morphological changes. Cbeta2 is a ubiquitously expressed protein with characteristic properties of a cAMP-dependent protein kinase catalytic subunit.

Myristoylated src-oncogene products are potently detected by the monoclonal antibody to the NH2-terminal myristoyl-Gly-Ser-Ser-Lys src-peptide

Monoclonal antibodies were raised against a synthetic NH2-terminal myristoyl tetrapeptide (N-myristoyl-Gly-Ser-Ser-Lys) which is characteristic of an NH2-terminal portion of pp60src, the transforming protein of src-oncogene. The antibody reacted with the albumin conjugated with both the N-myristoyl and N-lauroyl-tetrapeptides, but concentrations at which 50% of the immunoreaction was inhibited were 5 pmol for the N-myristoyl and 830 pmol for N-lauroyl tetrapeptidyl albumin. On the other hand, N-palmitoyl tetrapeptidyl and underivatized albumin, and Gly-Ser-Ser-Lys-Ser-Lys-Pro-Lys octapeptide had no effects. These results suggest a high affinity of the antibody for an N-myristoyl-Gly-Ser-Ser-Lys moiety. src-Oncogene products in Rous sarcoma virus-transformed cells and human colon carcinoma tumor cells were selectively identified as myristoylated pp60src by immunoprecipitation analyses with the antibody.

A novel antibody against a synthetic NH2-terminal myristoyl glycyl src peptide can detect pp60v-src, the transforming protein of Rous sarcoma virus

Novel antibodies were raised against a synthetic NH2-terminal myristoyl(Myr-) tetrapeptide(N-Myr-Gly-Ser-Ser-Lys) which is characteristic of an NH2-terminal portion of pp60v-src, the transforming protein of Rous sarcoma virus. Antisera raised against N-Myr-Gly-Ser-Ser-Lys-haemocyanin reacted with 125I-albumin conjugates with N-Myr-Gly-Ser-Ser-Lys. The immunoreaction was competed for by haemocyanin as well as albumin conjugated with this N-Myr-peptide, while underivatized proteins or an NH2-terminal octapeptide (Gly-Ser-Ser-Lys-Ser-Lys-Pro-Lys) had no effect. N-Myr-Gly-Ser-Ser-Lys-(125I)tyramine was also recognized by the antibody. The reaction was competed for by N-Myr-Gly-Ser-Ser-Lys, but not by Gly-Ser-Ser-Lys-Ser-Lys-Pro-Lys. These results suggest a high affinity of the antibody for an N-Myr-peptide moiety. The major (3H)myristate-labelled protein of an apparent molecular weight of 60,000 was detected from chick embryo fibroblasts transformed by Rous sarcoma virus (tsNY68). This protein was demonstrated to possess N-Myr-Gly-Ser-Ser-Lys by the immunoprecipitation and HPLC analyses. Furthermore, the entire circumference of the transformed cells was stained by the antibody upon an immunofluorescent microscopic observation. Thus, these results taken together indicate that the haptenic antibody raised against the myristoyl peptide is useful to detect pp60v-src protein.

Antibodies to an NH2-terminal myristoyl glycine moiety can detect NH2-terminal myristoylated proteins in the retrovirus-infected cells

Novel antibodies were raised against a synthetic NH2-terminal myristoyl glycine moiety which is characteristic of N-myristoyl-proteins. Antisera raised against N-myristoyl-Gly-hemocyanin reacted with N-myristoyl-Gly-[125I]albumin. The immunoreaction was competed for by albumin conjugated with N-myristoyl-glycine, while underivatized albumin had no effect. Of the [3H]myristate-labeled proteins detected, pp60v-src, which is a transforming protein of Rous sarcoma virus, and p19gag and p17gag, which are core proteins in the human T-cell leukemia virus and the human immunodeficiency virus, were identified as N-myristoylated proteins by the radioimmunoprecipitation analyses with the antibody.