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Electrostatic repulsion between molecules of like charge can be misinterpreted as binding
Author(s) -
Stemmer Paul,
Klee Claude B.
Publication year - 1990
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(90)80509-h
Subject(s) - chemistry , lysozyme , calmodulin , spermine , biophysics , static electricity , chelation , molecule , plasma protein binding , calcium binding protein , binding site , crystallography , calcium , biochemistry , inorganic chemistry , enzyme , biology , organic chemistry , electrical engineering , engineering
Spectroscopic methods have shown that Ca 2+ chelators interact with Ca 2+ ‐binding proteins. These spectral alterations have been interpreted as evidence for the binding of chelator by the proteins. We show by direct examination of EDTA interaction with calmodulin and α‐lactalbumin that these proteins repel EDTA rather than bind it. The repulsion is reduced by increased salt concentration but is unaffected by Ca 2+ binding to the proteins. The acidic protein, α‐lactalbumin, repells the negatively charged EDTA and inorganic phosphate whereas the basic protein, lysozyme, repells the positively charged spermine. Thus, spectroscopic changes induced by negatively charged Ca 2+ chelators on negatively charged Ca 2+ ‐binding proteins are due to electrostatic repulsion, and not to binding. These observations underscore the possible pitfalls of using spectroscopic methods alone to analyze protein‐ligand interactions.