Calcium-dependent metabolic regulations in prokaryotes indicate conserved nature of calmodulin gene.

Role of free calcium and calcium binding protein calmodulin as signal molecule in cellular regulation is well established in eukaryotes. However, reports on Ca(2+)-dependent processes and their inhibition by calcium and/or calmodulin antagonists indicate towards the presence of calmodulin in prokaryotes as well. The common evolutionary origin of pro- and eukaryotes and many examples of evolutionary conservation of structure and functions support the contention of such conservation of the role of Ca2+ and calmodulin. Eukaryotic calmodulin (CaM) contains four structurally and functionally similar Ca2+ domains named I, II, III and IV. Each Ca2+ binding loop consists of 12 amino acid residues with ligands arranged spatially to satisfy the octahedral symmetry of Ca2+ binding. Plant calmodulin differ from vertebrate ones in 13 to 14 amino acid positions of which nine occur at -COOH- terminal half. Differences between protozoan and mammalian CaM also occur mostly in the same half. Isolation and characterization, although to a little extent, of CaM-like proteins from bacteria and cyanobacteria and their comparison with CaMs from diverse origin suggest high degree of conservation. Non-bulky amino acids like glycine, alanine and serine with low specific rotation are present in greater number in the primitive form of calmodulin and have been significantly reduced in highly evolved form of calmodulin, suggesting that their requirement was insignificant and were eliminated from EF hand structure during evolution. However, amino acids like glutamate/glutamine and aspartate/asparagine were highly conserved and did not show any major change in their frequency since their positions are too significant in calcium binding domain. While the number of positively charged amino acids like arginine and leucine was increased, histidine containing weakly ionized group and having a significant buffering capacity was reduced to a major extent, further suggesting that the acidic nature of calmodulin protein has been maintained during evolution. Thus it is now clear that the entire superfamily of Ca2+ binding proteins have arisen from a common genetic ancestry. Two successive tandem duplications of gene encoding a single domain containing protein of 30-40 residues gave rise to a four domain molecule from which this family was then derived.

Phytolectins: natural molecules with immense biotechnological potential.

Lectins are structurally diverse, carbohydrate binding proteins that bind reversibly to specific mono- or oligosaccharides. Their abundance in the plant kingdom suggest that they have diverse roles to perform. They serve as recognition factor between symbiotic nitrogen fixing bacteria and host plants, as a deterrent to phytopathogens like fungi, insects, and animals, as storage protein and as an aid in sexual reproduction in Chlamydomonas, amongst others. The possible application of lectins as a factor in increasing soil fertility and as a biopesticide by genetically engineered organisms is yet to be fully explored by the biotechnologists. However, they are being used by the biomedical scientists and biochemists in blood typing and stimulation of cells for chromosome analysis and gene mapping, in cell separation, identification of complex glycoproteins and typing of bacteria. Cell targeting by lectins in cancer therapy is still in its infancy. This review gives an insight into the potential of these wonder biomolecules in agriculture, biochemistry, cell biology and medicine for the benefit of mankind.

Phaseolus vulgaris L. var. HUR 15--a potential indigenous source for commercial PHA preparation.

Mitogenic potential of the partially purified lectin from P. vulgaris isolated by ammonium sulphate precipitation was assessed by lymphocyte transformation test (LTT) and was compared with three commercially available phytohemagglutinins (PHA). The blast inducing capacity and mitotic index analysis revealed that this preparation has potential to be used in the indigenous commercial production of PHA which is routinely used for human chromosomal studies from the peripheral blood culture at, at present, is imported.

Protein profile and stimulation potential of partially purified lectins from two varieties of Phaseolus vulgaris L.

Phytohaemagglutinin obtained from P. vulgaris is a commonly used mitogen in lymphocyte cultures. The mitogenic potential of different cultivars of P. vulgaris vary. The present investigation encompasses the characterization of partially purified lectins from two varieties of P. vulgaris on the basis of their protein profile, lymphocyte transformation test by light and scanning electron microscopy and incorporation of radioactive thymidine.