Abstract:
:Twenty-seven mutant bacteriorhodopsin's were screened to determine the PKa for reversal of the permanent electric dipole moment. The photoelectric response of an aqueous purple-membrane suspension was used to determine the direction of the purple-membrane dipole moment as a function of pH. The pK(a) for the dipole reversal of wild-type bacteriorhodopsin is 4.5. Six of the 27 mutant bacteriorhodopsin's were found to have a pK(a) for dipole reversal larger than that of wild-type bacteriorhodopsin. Two of these mutants, L93T and L93W, involve a neutral amino acid substitution in the interior of the protein. The direction of the purple-membrane permanent electric dipole moment is determined by the purple-membrane surface charge asymmetry. We conclude that these two substitutions, which do not involve charge replacement, alter the pK(a) for the reversal of the purple-membrane surface charge asymmetry. We suggest that these changes to the pK(a) are due to altered protein folding at the surface of the purple-membrane induced by single-site substitutions in the protein interior.
journal_name
Biophys Jjournal_title
Biophysical journalauthors
Hsu KC,Rayfield GW,Needleman Rdoi
10.1016/S0006-3495(96)79802-8subject
Has Abstractpub_date
1996-05-01 00:00:00pages
2358-65issue
5eissn
0006-3495issn
1542-0086pii
S0006-3495(96)79802-8journal_volume
70pub_type
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