TY  - JOUR
AU  - Dutta, A.
AU  - Tirupula, K.C.
AU  - Alexiev, U.
AU  - Klein-Seetharaman, J.
TI  - Characterization of membrane protein non-native states. 1. Extent of unfolding and aggregation of rhodopsin in the presence of chemical denaturants
JO  - Biochemistry
VL  - 49
SN  - 0006-2960
CY  - Columbus, Ohio
PB  - American Chemical Society
M1  - PreJuSER-13097
SP  - 6317 - 6328
PY  - 2010
N1  - This work was in part supported by National Science Foundation CAREER Grant CC044917, National Institutes of Health Grant NLM108730, and the Pennsylvania Department of Health.
AB  - Little is known about the general folding mechanisms of helical membrane proteins. Unfolded, i.e., non-native states, in particular, have not yet been characterized in detail. Here, we establish conditions under which denatured states of the mammalian membrane protein rhodopsin, a prototypic G protein coupled receptor with primary function in vision, can be studied. We investigated the effects of the chemical denaturants sodium dodecyl sulfate (SDS), urea, guanidine hydrochloride (GuHC1), and trifluoroacetic acid (TFA) on rhodopsin's secondary structure and propensity for aggregation. Ellipticity at 222 nm decreases in the presence of maximum concentrations of denaturants in the order TFA > GuHCl > urea > SDS + urea > SDS. Interpretation of these changes in ellipticity in terms of helix loss is challenged because the addition of some denaturants leads to aggregation. Through a combination of SDS PAGE, dependence of ellipticity on protein concentration, and ID H-1 NMR we show that aggregates form in the presence of GuHCI, TEA, and urea but not in any concentration of SDS, added over a range of 0.05%-30%. Mixed denaturant conditions consisting of 3% SDS and 8 M urea, added in this order, also did not result in aggregation. We conclude that SDS is able to prevent the exposure of large hydrophobic regions present in membrane proteins which otherwise leads to aggregation. Thus, 30% SDS and 3% SDS + 8 M urea are the denaturing conditions of choice to study maximally unfolded rhodopsin without aggregation.
KW  - J (WoSType)
LB  - PUB:(DE-HGF)16
UR  - <Go to ISI:>//WOS:000280416100004
DO  - DOI:10.1021/bi100338e
UR  - https://juser.fz-juelich.de/record/13097
ER  -