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A mathematical model for metal affinity protein partitioning
Author(s) -
Suh SungSup,
Arnold Frances H.
Publication year - 1990
Publication title -
biotechnology and bioengineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.136
H-Index - 189
eISSN - 1097-0290
pISSN - 0006-3592
DOI - 10.1002/bit.260350705
Subject(s) - chemistry , metal , biochemical engineering , computational biology , biological system , biology , organic chemistry , engineering
A mathematical model of metal affinity partitioning has been derived and used to describe protein partitioning in Cu (II)PEG/dextran systems. A working model has been extended to account for inhibition, which for metal affinity extraction is the inhibition of protein‐metal binding by hydrogen ion. PEG/dextran partitioning experiments were performed on four proteins, tuna heart cytochrome c, Candida krusei cytochrome c, horse myoglobin, and sperm whale myoglobin. The partition coefficients for these proteins are increased by the addition of Cu (II)PEG‐IDA, due to the affinity between the chelated copper atom and metal‐coordinating histidine residues on the protein surface. The results of experiments to determine the effects of the number of binding sites on the protein, the copper concentration, and pH on partitioning are all well‐described by the mathematical model. The pK a value of the metal binding site was determined to be 6.5, which is in the range of pK a values commonly observed for surface histidines. The average association constant for the binding of Cu (II)PEG‐IDA to accessible histidines was found to be 4.5 × 10 3 . This value is comparable to stability constants measured by conventional potentiometry techniques for analogous small complexes.