Amino acid sequence of a low molecular weight, high affinity calcium-binding protein from the optic lobe of the squid Loligo pealei

Calretinin distribution in the octopus brain: an immunohistochemical and in situ hybridization histochemical analysis

The distribution of calretinin containing neurons examined by in situ hybridization mapping was compared with that obtained by immunocytochemistry in the brain of octopus. Results revealed a close correspondence between the two types of investigations. Western blot analysis disclosed a 29 kDa protein immunostained with anti-calretinin antibody. Calretinin containing neurons were localized mainly in the cortex of octopus lobes, including the vertical, frontal, basal, buccal, palliovisceral, pedal and branchial, with variations of staining intensity and density of immunoreactive cells. The amacrine cells surrounding calretinin containing neuronal bodies of the cortex were also labeled unlike the glial cells. The close correspondence of blotting analysis, immunocytochemistry and in situ hybridization indicates with no doubt that calretinin, like other calcium-binding proteins previously studied, is also present in the nervous system of cephalopods. Furthermore, although recent findings localize calretinin also in endocrine glands, the presence of this calcium-binding protein in the brain of octopus indicates that calretinin appeared early in the phylogeny as a neuronal protein already in invertebrates.

Sarcoplasmic calcium-binding proteins in Aplysia nerve and muscle cells

Muscle (body wall, buccal mass, heart) and neural tissue of the marine mollusc Aplysia californica was analysed for calcium-binding proteins using transblot/45Ca overlay, Western blotting and two-dimensional polyacrylamide gel electrophoresis, and several low molecular weight calcium-binding proteins were identified. Our results that Aplysia muscle contains an abundant protein with a M(r) of approximately 20,000 with strong 45Ca(2+)-binding ability and cross-reactivity to antibodies against the sarcoplasmic calcium-binding protein isoform II (SCP II) from Amphioxus. Immunocytochemical studies revealed that isoforms of SCP are distributed in a tissue-specific manner, SCP II-like protein is exclusively present in muscle fibres closely associated with the contractile machinery, whereas the isoform I (SCP I-like protein) is exclusively present in a subset of neurons, suggesting a function in their calcium regulation. In addition, a novel 45Ca(2+)-binding protein of M(r) 43,000, pl 4.7, was found in muscle and in neurons. A third protein of M(r) 40,000, pl 4.8, cross-reacts with anti-parvalbumin and anti-calbindin D-28K antibodies.

Evolution of EF-hand calcium-modulated proteins. I. Relationships based on amino acid sequences

The relationships among 153 EF-hand (calcium-modulated) proteins of known amino acid sequence were determined using the method of maximum parsimony. These proteins can be ordered into 12 distinct subfamilies--calmodulin, troponin C, essential light chain of myosin, regulatory light chain, sarcoplasmic calcium binding protein, calpain, aequorin, Stronglyocentrotus purpuratus ectodermal protein, calbindin 28 kd, parvalbumin, alpha-actinin, and S100/intestinal calcium-binding protein. Eight individual proteins--calcineurin B from Bos, troponin C from Astacus, calcium vector protein from Branchiostoma, caltractin from Chlamydomonas, cell-division-cycle 31 gene product from Saccharomyces, 10-kd calcium-binding protein from Tetrahymena, LPS1 eight-domain protein from Lytechinus, and calcium-binding protein from Streptomyces--are tentatively identified as unique; that is, each may be the sole representative of another subfamily. We present dendrograms showing the relationships among the subfamilies and uniques as well as dendrograms showing relationships within each subfamily. The EF-hand proteins have been characterized from a broad range of organismal sources, and they have an enormous range of function. This is reflected in the complexity of the dendrograms. At this time we urge caution in assigning a simple scheme of gene duplications to account for the evolution of the 600 EF-hand domains of known sequence.