The basis for the unusual properties of the catalytic subunit (C) of ram sperm cAMP-dependent protein kinase was investigated. Ram sperm C was purified and found by mass spectrometry (MS) to be approximately 890 Da smaller than Calpha, the predominant somatic isoform. Partial internal amino acid sequence from ram sperm C was an exact match to that of bovine Calpha, but differed from the predicted sequences for the Cbeta and Cgamma isoforms. MS analysis of 2-nitro-5-thiocyanatobenzoic acid fragments showed that the mass difference originated in the amino-terminal region. A unique blocked amino-terminal fragment was isolated from sperm C and sequenced by a combination of tandem mass spectrometry and Edman degradation of a subfragment. The results revealed that the amino-terminal myristate and the first 14 amino acids of Calpha are replaced by an amino-terminal acetate and six different amino acids in sperm C. The predicted mass difference due to these changes is 899 Da. The region of homology between sperm C and Calpha begins at the exon 1/exon 2 boundary in Calpha, suggesting that sperm C results from use of an alternate exon 1 in the Calpha gene. The different amino terminus of sperm C may be related to a unique requirement for localization of the "free" C subunit within the sperm flagellum.
| Predicate | Object |
|---|---|
| rdf:type | |
| rdfs:comment |
The basis for the unusual properties of the catalytic subunit (C) of ram sperm cAMP-dependent protein kinase was investigated. Ram sperm C was purified and found by mass spectrometry (MS) to be approximately 890 Da smaller than Calpha, the predominant somatic isoform. Partial internal amino acid sequence from ram sperm C was an exact match to that of bovine Calpha, but differed from the predicted sequences for the Cbeta and Cgamma isoforms. MS analysis of 2-nitro-5-thiocyanatobenzoic acid fragments showed that the mass difference originated in the amino-terminal region. A unique blocked amino-terminal fragment was isolated from sperm C and sequenced by a combination of tandem mass spectrometry and Edman degradation of a subfragment. The results revealed that the amino-terminal myristate and the first 14 amino acids of Calpha are replaced by an amino-terminal acetate and six different amino acids in sperm C. The predicted mass difference due to these changes is 899 Da. The region of homology between sperm C and Calpha begins at the exon 1/exon 2 boundary in Calpha, suggesting that sperm C results from use of an alternate exon 1 in the Calpha gene. The different amino terminus of sperm C may be related to a unique requirement for localization of the "free" C subunit within the sperm flagellum.
|
| skos:exactMatch | |
| uniprot:name |
J. Biol. Chem.
|
| uniprot:author |
Leszyk J.D.,
Nuwaysir L.M.,
San Agustin J.T.,
Witman G.B.
|
| uniprot:date |
1998
|
| uniprot:pages |
24874-24883
|
| uniprot:title |
The catalytic subunit of the cAMP-dependent protein kinase of ovine sperm flagella has a unique amino-terminal sequence.
|
| uniprot:volume |
273
|
| dc-term:identifier |
doi:10.1074/jbc.273.38.24874
|