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ESR studies on the effect of ionic radii on displacement of Mn 2+ bound to a soluble β‐galactoside binding hepatic lectin
Author(s) -
Kayestha Rajeev,
Hajela Krishnan
Publication year - 1995
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(95)00673-w
Subject(s) - ionic radius , chemistry , divalent , electron paramagnetic resonance , metal , binding site , lectin , crystallography , metal ions in aqueous solution , galactoside , ionic bonding , inorganic chemistry , ion , stereochemistry , biochemistry , nuclear magnetic resonance , organic chemistry , physics , enzyme
Binding of divalent metal ions to hepatic soluble β‐galactoside binding lectin was studied using electron spin resonance (ESR) spectroscopy. The Mn 2+ bound to hepatic lectin could be displaced by Mg 2+ , Cu 2+ , Ni 2+ and Ca 2+ but not by Sr 2+ . As the ionic radii of Mg 2+ (0.65 Å), Cu 2+ (0.73 Å) and Ni 2+ (0.72 Å) are appreciably smaller than Ca Mn 2+ binding site is more accessible to Mg 2+ , Cu 2+ , and Ni 2+ as compared to Ca 2+ , the ionic radius of Mn 2+ being 0.80 Å. Sr 2+ with an ionic radius of 1.13 is thus unable to displace bound Mn 2+ . Surprisingly, the presence of specific sugars like α‐lactose, or α‐ d ‐galactose facilitated the displacement of bound Mn 2+ by metal ions whereas non‐specific sugars, i.e. α‐ d ‐glucose, β‐ d ‐fructose and α‐ d ‐ribose had no effect. It appears that minor perturbations in the saccharide binding site significantly affect the ability of the metal binding site to ligate bivalent metals.