Electrostatic stabilization in sperm whale and harbor seal myoglobins. Identification of groups primarily responsible for changes in anchoring of the A helix.
The compact, largely helical structure of sperm whale and harbor seal myoglobins undergoes an abrupt one-step transition between pH 4.5 and 3.5 as monitored by changes in either the heme Soret band absorbance or circular dichroism probes of secondary structure, for which a modified Tanford-Kirkwood...
| Main Authors: | , , , , |
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| Format: | Text |
| Language: | English |
| Published: |
1980
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| Subjects: | |
| Online Access: | http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1327257 http://www.ncbi.nlm.nih.gov/pubmed/7248465 |
| Summary: | The compact, largely helical structure of sperm whale and harbor seal myoglobins undergoes an abrupt one-step transition between pH 4.5 and 3.5 as monitored by changes in either the heme Soret band absorbance or circular dichroism probes of secondary structure, for which a modified Tanford-Kirkwood theory provides identification of certain dominant electrostatic interactions responsible for the loss of stability. A similar treatment permits identification of the electrostatic interactions primarily responsible for a process in which the anchoring of the A helix to other parts of the molecule is weakened. This process is detected with both myoglobins, in a pH range approximately 1 unit higher than the onset of the overall unfolding process, through changes in the circular dichroic spectra near 295 nm which correspond to the L1 O-O band of the only two tryptophan residues in these proteins, residues 7 and 14. In each case protonation of certain sites in neighboring parts of the molecule can be identified as producing destabilizing interactions with components of the A helix, particularly with lysine 6. |
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