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Hyperthermal stability of neuroglobin and cytoglobin
Author(s) -
Hamdane Djemel,
Kiger Laurent,
Dewilde Sylvia,
Uzan Julien,
Burmester Thorsten,
Hankeln Thomas,
Moens Luc,
Marden Michael C
Publication year - 2005
Publication title -
the febs journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.981
H-Index - 204
eISSN - 1742-4658
pISSN - 1742-464X
DOI - 10.1111/j.1742-4658.2005.04635.x
Subject(s) - neuroglobin , histidine , globin , chemistry , hexa , thermal stability , crystallography , biophysics , stereochemistry , biochemistry , hemoglobin , biology , amino acid , organic chemistry
Neuroglobin (Ngb) and cytoglobin (Cygb), recent additions to the globin family, display a hexa‐coordinated (bis‐histidyl) heme in the absence of external ligands. Although these proteins have the classical globin fold they reveal a very high thermal stability with a melting temperature ( T m ) of 100 °C for Ngb and 95 °C for Cygb. Moreover, flash photolysis experiments at high temperatures reveal that Ngb remains functional at 90 °C. Human Ngb may have a disulfide bond in the CD loop region; reduction of the disulfide bond increases the affinity of the iron atom for the distal (E7) histidine, and leads to a 3 °C increase in the T m for ferrous Ngb. A similar T m is found for a mutant of human Ngb without cysteines. Apparently, the disulfide bond is not involved directly in protein stability, but may influence the stability indirectly because it modifies the affinity of the distal histidine. Mutation of the distal histidine leads to lower thermal stability, similar to that for other globins. Only globins with a high affinity of the distal histidine show the very high thermal stability, indicating that stable hexa‐coordination is necessary for the enhanced thermal stability; the CD loop which contains the cysteines appears as a critical region in the neuroglobin thermal stability, because it may influence the affinity of the distal histidine.