Protein sequence determination by ESI-MS and LSI-MS tandem mass spectrometry: parvalbumin primary structures from cat, gerbil and monkey skeletal muscle

Identification of parvalbumin alpha in bovine hypothalamus: a partial primary structure

In the course of the study of structure-functional properties and molecular mechanisms of neuropeptides and of low molecular weight proteins of the central nervous system we succeeded in isolating from the soluble fraction of bovine hypothalamus a protein having M(r) 11897.3, according to mass spectral analysis. The purification procedure was mainly based on reversed phase HPLC. As the N-terminus of the molecule was found to be blocked, we have subjected it to CNBr degradation. By Edman microsequence analysis of the peptide fragments and by data base searching the isolated substance was identified as parvalbumin alpha (PRVA)-one of the calcium-binding proteins. However, its primary structure was found not to be identical to that of the known PRVAs from other sources. One of the features of PRVA is its stability. Being subjected to an exhausting purification procedure it retains its complete structure. As neuropeptides and low molecular weight proteins are found to be polyfunctional, a central question concerns the biological role of PRVAs in terms of "where and when" they express their action.

Molecular cloning and expression of alpha parvalbumin in the guinea pig cochlea

We have cloned and sequenced an alpha parvalbumin cDNA from the guinea pig cochlea. The deduced amino acid sequence shows greater identity with the rabbit sequence (86.3%) than with other mammalian sequences (< 82%). Using in situ hybridization and immunohistochemistry, alpha parvalbumin mRNA and protein were found in primary auditory neurons and inner hair cells, in agreement with RT-PCR data showing alpha parvalbumin mRNA expression in the spiral ganglion and the organ or Corti.

The surface evoked potential and parvalbumin-immunoreactivity in the somatosensory cortex of the developing rat

The development of the rat somatosensory system was followed electrophysiologically and immunohistochemically. In the surface evoked potential elicited in the primary somatosensory cortex by electrical stimulation of the whisker C3 follicle, a short-latency positive wave was first recorded on postnatal Day 2. A long-latency positive wave was recorded in some pups on postnatal Day 7 and in most pups on postnatal Day 8. On postnatal Day 10, a P/N complex appeared between the short- and long-latency positive waves. Parvalbumin, believed to appear with functional maturation, appeared mainly after postnatal Day 7 in Layer V in the underlying area, although a few weakly stained cells appeared on postnatal Day 5. On postnatal Day 10, weakly stained cells appeared in the area containing barrels; their staining increased with time. In this system, electrophysiological and immunohistochemical parameters changed by the 3rd postnatal week with the most marked changes occurring within 2 postnatal weeks.

A novel EF-hand Ca(2+)-binding protein from abdominal muscle of crustaceans with similarity to calcyphosine from dog thyroidea

The amino acid sequence of a novel EF-hand Ca(2+)-binding protein from the abdominal muscle of the crayfish, Orconectes limosus, has been elucidated by tandem mass spectrometry and automated Edman degradation. The name CCBP-23 (23-kDa crustacean Ca(2+)-binding protein) is proposed. The protein can also exist as a disulfide-linked homodimer. The sequence of the monomeric form spans 200 residues with an acetylated N-terminal Ser and reveals four EF-hand domains. The 174-mass-unit difference between the calculated average molecular mass of 22,669.6 Da deduced from the sequence and the obtained electrospray ionization mass spectroscopy (ESI-MS) mass of 22,844 Da has not yet been explained. Partial sequence analysis (137 residues) of CCBP-23 from the lobster, Homarus americanus, showed a sequence identity of 74% with the crayfish protein. Homology searches revealed a 44% sequence identity of CCBP-23 from crayfish to calcyphosine, a Ca(2+)-binding protein from dog thyroidea (Lefort et al., 1989). Although CCBP-23 also shows a 44% identity to R2D5 antigen (Nemoto et al., 1993), we believe that both proteins represent two distinct subgroups within the family of EF-hand proteins.

Characterization and primary structure of amphioxus troponin C

Troponin C (TnC) from amphioxus (Protochordate) was purified and its primary structure determined. Unlike the case of vertebrates and other invertebrates, amphioxus TnC is found in the soluble fraction after extractions at physiological ionic strength in the presence of Ca2+. Edman sequencing combined with mass spectroscopy indicate that the protein contains 163 amino acid residues. It possesses an acetylated N-terminus (although a small percentage has a free Ser N-terminus) and either epsilon-N-methyllysine or epsilon-N-dimethyllysine in position 20. It displays about 50% sequence identity with vertebrate skeletal-muscle and cardiac-muscle TnC, 44% with TnC of sea squirt, also a Protochordate, and 30% with other invertebrate TnC. Like vertebrate TnC, amphioxus TnC contains a N-terminal alpha-helix plus the usual four ancestral Ca(2+)-binding regions, but analysis of the sequence suggests that the fourth site is not functional. Flow dialysis shows that amphioxus TnC binds three Ca2+ with the mean apparent affinity constant K' of 3.4 +/- 1.5 10(5) M-1. No cooperativity exists between the sites, and the presence of up to 10 mM Mg2+ does not influence the Ca(2+)-binding isotherm, indicating that the metal-binding sites are Ca(2+)-specific at physiological Mg2+ concentrations. It forms a Ca(2+)-dependent, 1:1 complex with melittin and rabbit or crayfish troponin I (TnI). Amphioxus TnC possesses one Trp residue in position 151 and one at the C-terminus. Trp fluorescence suggests that one or both residues are solvent-exposed in the metal-free form and efficiently shielded in the Ca2+ form. Although Mg2+ has no effect on the Ca2+ binding, the Trp fluorescence is influenced by millimolar Mg2+, suggesting the presence of one or more independent Mg(2+)-binding site(s). A phylogenetic analysis clearly shows that amphioxus TnC is positioned on the branch of the Chordates, but at a distance from the vertebrate TnC. Its place on the phylogenetic tree is in accordance with the consensus evolutionary phylogeny.

Human alpha and beta parvalbumins. Structure and tissue-specific expression

alpha and beta parvalbumins are Ca(2+)-binding proteins of the EF-hand type. We determined the protein sequence of human brain alpha parvalbumin by mass spectrometry and cloned human beta parvalbumin (or oncomodulin) from genomic DNA and preterm placental cDNA. beta parvalbumin differs in 54 positions from alpha parvalbumin and lacks the C-terminal amino acid 109. From MS analyses of alpha and beta parvalbumins we conclude that parvalbumins generally lack posttranslational modifications. alpha and beta parvalbumins were differently expressed in human tissues when analyzed by immunoblotting and polymerase-chain-reaction techniques. Whereas alpha parvalbumin was found in a number of adult human tissues, beta parvalbumin was restricted to preterm placenta. The pattern of alpha parvalbumin expression also differs in man compared to other vertebrates. For example, in rat, alpha parvalbumin was found in extrafusal and intrafusal skeletal-muscle fibres whereas, in man, alpha parvalbumin was restricted to the muscle spindles. Different functions for alpha and beta parvalbumins are discussed.