Journal of Biochemistry Advance Access originally published online on September 20, 2006
Journal of Biochemistry 2006 140(5):649-656; doi:10.1093/jb/mvj192
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© 2006 The Japanese Biochemical Society.
ARTICLE |
Effect of Amino Acid Replacements on the Structural Stability of Fish Myoglobin

Laboratory of Aquatic Molecular Biology and Biotechnology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Bunkyo, Tokyo 113-8657
To whom correspondence should be addressed: Phone/Fax: +81-3-5841-7521, E-mail: aochiai{at}mail.ecc.u-tokyo.ac.jp
Structural stabilities of myoglobin (Mb) from several fish (scombridae) species differ significantly, although their amino acid sequence identity is very high (>95%), suggesting that only a few substitutions greatly affect the stability of Mb. Accordingly, recombinant Mbs with point mutation(s) derived from bigeye tuna Mb cDNA were expressed as GST-fusion proteins in the soluble fractions of Escherichia coli. After removal of the GST segment, the stability of five mutants, namely, P13A, I21M, V57I, A62G, and I21M/V57I, together with the wild type (WT) were investigated, taking temperature dependency of
-helical content and denaturant concentration dependency of Soret band absorbance as parameters. As a result, the stability of P13A against denaturants and its
-helical content at 10°C was found to be the highest among the mutants, whereas those of A62G were the lowest. The stabilities of V57I and I21M/V57I were higher than that of WT, though that of I21M was nearly the same as WT. These findings suggest that the structural stability of fish Mb is tuned up only by the substitutions of a few amino acid residues located in the
-helical segments forming the hydrophobic heme pocket.
* Present address: Laboratory of Peptide Biosignal Engineering, Mitsubishi Kagaku Institute of Life Sciences, Machida, Tokyo 195-8511.