Model for the structure of bacteriorhodopsin based on high-resolution electron cryo-microscopy.

Structure of purple membrane from halobacterium halobium: recording, measurement and evaluation of electron micrographs at 3.5 Å resolution

https://www.zora.uzh.ch/id/eprint/65956/1/Henderson_et_al._2012.pdf

Outcome of the First Electron Microscopy Validation Task Force Meeting

A prediction algorithm based on physical characteristics of the twenty amino acids and refined by comparison to the proposed bacteriorhodopsin structure was devised to delineate likely membrane-buried regions in the primary sequences of proteins known to interact with the lipid bilayer. Application of the method to the sequence of the carboxyl terminal one-third of bovine rhodopsin predicted a membrane-buried helical hairpin structure. With the use of lipid-buried segments in bacteriorhodopsin as well as regions predicted by the algorithm in other membrane-bound proteins, a hierarchical ranking of the twenty amino acids in their preferences to be in lipid contact was calculated. A helical wheel analysis of the predicted regions suggests which helical faces are within the protein interior and which are in contact with the lipid bilayer.

https://www.biosyn.com/Images/ArticleImages/pdf/Structural%20Prediction%20of%20Membrane-Bound%20Proteins.pdf

Structural Prediction of Membrane‐Bound Proteins

1,2-Bis(9,10-dibromooleoyl)phosphatidylcholine (BRPC) has been prepared from dioleoylphosphatidylcholine (DOPC). It is shown that the gel to liquid-crystalline phase transition for BRPC occurs below ca. 5 degrees C and that the motional properties of bilayers of BRPC and DOPC as detected by spin-labeled fatty acids are similar. The ATPase activities of the (Ca2+-Mg2+)-ATPase from rabbit muscle sarcoplasmic reticulum reconstituted with BRPC and DOPC are similar. The brominated lipid quenches the fluorescence of the ATPase and can be used to determine selectivity of lipid binding to the ATPase. We show that there is little selectivity on the basis of fatty acyl chain length. Binding constants for phosphatidylcholines and phosphatidylserines are similar in the absence of calcium, although that for phosphatidylserine decreases in the presence of calcium. Phosphatidylethanolamines binds less strongly than phosphatidylcholines, although the difference is small. The largest difference in binding constants is seen between phosphatidylcholines in the gel and liquid-crystalline phases, with a distribution coefficient of 30 in favor of the liquid-crystalline phase. It is shown that the distribution of the ATPase in mixtures of dipalmitoylphosphatidylcholine and BRPC can be understood in terms of the phase diagram for this mixture of lipids. Activities of the ATPase in the presence of mixtures of lipids can be explained in terms of the relative binding constants obtained from the fluorescence experiments.

Lipid selectivity of the calcium and magnesium ion dependent adenosine triphosphatase, studied with fluorescence quenching by a brominated phospholipid

Steven B. Hayward

Papers

Projected structure of purple membrane determined to 3.7 A resolution by low temperature electron microscopy.

Location of an extrinsic label in the primary and tertiary structure of bacteriorhodopsin