Molecular cloning, expression, and cytokinin (6-benzylaminopurine) antagonist activity of peanut (Arachis hypogaea) lectin SL-I

Abstract

Isolation and purification of a alpha-methyl-mannoside specific lectin (SL-I) of peanut was reported earlier [Singh and Das (1994) Glycoconj J 11:282-285]. Native SL-I is a glycoprotein having approximately 31 kDa subunit molecular mass and forms dimer. The gene encoding this lectin is identified from a 6-day old peanut root cDNA library by anti-SL-I antibody and N-terminal amino acid sequence homology to the native lectin. Nucleotide sequence derived amino acid sequence of the re-SL-I shows amino acid sequence homology with the N-terminal and tryptic digests' amino acid sequence of the native SL-I (nSL-I). Presence of a putative glycosylation (QNPS) site and a hydrophobic adenine-binding (VLVSYDANS) site is also identified in SL-I. Homology modeling of the lectin suggests it to be an archetype of legume lectins. It is expressed as a approximately 30 kDa apoprotein in E. coli and has the carbohydrate specificity and secondary structure identical to its natural counterpart. The lectin SL-I inhibits cytokinin 6-benzylaminopurine (BA)-induced "delayed leaf senescence" and "cotyledon expansion". Equilibrium dialysis revealed a single high-affinity binding site for adenine (7.6 x 10(-6 )M) and BA (1.09 x 10(-5 )M) in the SL-I dimer and thus suggesting that the cytokinin antagonist effect of SL-I is mediated by the direct interaction of SL-I with BA.

Cathepsin B cysteine protease gene is upregulated during leaf senescence and exhibits differential expression behavior in response to phytohormones in Picrorhiza kurrooa Royle ex Benth.

“…Goldthwaite and Laetsch (1967) analyzed the regulation of senescence of bean leaf discs in response to 6-BAP and found that 6-BAP reduced the loss of chlorophyll and protein from the leaf discs. Similarly, cytokinins (kinetin and 6-BAP) were effective in retarding senescence in leaf discs of Rumex (Goldthwaite and Laetsch, 1968) and N. tabacum (Pathak et al, 2006). Thus the present findings suggest that the association of cpcb with leaf senescence in Picrorhiza might also be regulated through cytokinin.…”

Interaction of Wheat Germ Agglutinin with Porphyrin Compounds—Potential Anticancer Agents

“…Recently, additionally to their saccharide specificity, it has been found that many plant lectins have hydrophobic sites for hydrophobic non-carbohydrate compounds (4,10,16,21,24,26,29). It is supposed that they are biologically relevant which is shown by their higher affinity for hydrophobic ligands than to carbohydrate ones.…”

Tumor-specific protein human galectin-1 interacts with anticancer agents

“…1 Recently, in addition to their carbohydrate-binding capacity, it has been discovered that some plant lectins have hydrophobic sites for adenine and physiological compounds. [2][3][4][5][6][7][8] The affinity towards these physiological non-carbohydrate ligands was higher than their affinity for carbohydrates indicating that the interaction with hydrophobic ligands may be biologically relevant. Similarly, some animal lectins have non-carbohydrate-binding domains, [9][10][11] and it is shown that they bind non-carbohydrate ligands through hydrophobic interactions.…”