COMPLETE IDENTIFICATION OF C=O STRETCHING VIBRATIONAL BANDS OF PROTONATED ASPARTIC-ACID RESIDUES IN THE DIFFERENCE INFRARED-SPECTRA OF M-INTERMEDIATE AND N-INTERMEDIATE VERSUS BACTERIORHODOPSIN

Citation
J. Sasaki et al., COMPLETE IDENTIFICATION OF C=O STRETCHING VIBRATIONAL BANDS OF PROTONATED ASPARTIC-ACID RESIDUES IN THE DIFFERENCE INFRARED-SPECTRA OF M-INTERMEDIATE AND N-INTERMEDIATE VERSUS BACTERIORHODOPSIN, Biochemistry, 33(11), 1994, pp. 3178-3184
Citations number
31
Categorie Soggetti
Biology
Journal title
ISSN journal
00062960
Volume
33
Issue
11
Year of publication
1994
Pages
3178 - 3184
Database
ISI
SICI code
0006-2960(1994)33:11<3178:CIOCSV>2.0.ZU;2-V
Abstract
Fourier transform infrared difference spectra were obtained for the M and N intermediates versus light-adapted bacteriorhodopsin (BR) with s ite-directed mutant proteins in which aspartic acid residues at positi ons 96 and 115 were replaced by asparagine. The positive and negative bands at 1740 and 1732 cm(-1) in the M/BR spectrum are shown to be the superposition of bands due to C=O stretching vibrations of Asp-96 and Asp-115 (a positive band at 1736 cm(-1) and a negative band at 1742 c m(-1) of Asp-96, and a positive band at 1742 cm(-1) and a negative ban d at 1734 cm(-1) of Asp-115). The positive band at 1738 cm(-1) and the negative band at 1734 cm(-1) in the N/BR spectrum are attributed to A sp-115. On the basis of these results, Asp-115 is protonated in M and N as well as in the ground state. On the other hand, no bands correspo nding to Asp-212 were found in the region of protonated carboxylic aci d vibration, indicating that Asp-212 remains unprotonated in M and N. The frequencies of the C=O stretching modes of protonated Asp-96 and A sp-115 change in the opposite direction in the BR-to-M conversion rela tive to the shifts in the BR-to-L conversion, indicating different env ironmental changes for these residues in L and M.