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Biomedical subjects

G Vanderkooi

Publications and source records attributed to G Vanderkooi.

At least 37 records · Page 2Linked to original sources
PubMed1973

Evidence for boundary lipid in membranes.

Cytochrome oxidase (EC 1.9.3.1) isolated from beef-heart mitochondria with an appropriate phospholipid content forms vesicular structures. Lipid-protein interactions in this model membrane system were studied with the lipid spin label, 16-doxylstearic acid. As the phospholipid/protein ratio is varied, two spectral components are observed. At low phospholipid/protein ratios (</=0.19 mg of phospholipid per mg of protein) the lipid spin label is highly immobilized. At higher phospholipid content an additional component characteristic of fluid lipid bilayers is evident. By summation of digitalized spectra and subsequent integration it was shown that all composite spectra could be approximated by assuming only two components are present, and that the amount of phospholipid bound to the protein is independent of the extent of the fluid bilayer region. The experimentally determined amount of phospholipid for maximum occupancy of protein-bound sites is about 0.2 mg of phospholipid per 1.0 mg of protein. Calculations show that this ratio is consistent with a single layer of phospholipid surrounding the protein complex. The data are interpreted as evidence for a boundary of immobilized lipid between the hydrophobic protein and adjacent fluid bilayer regions in this membrane model system.

Animals↗
PubMed1972

The low polarity of many membrane proteins.

The polarities of a large number of soluble and membrane proteins have been calculated by summing the mole fractions of polar amino acids. It was found that 85% of the 205 soluble proteins considered in this study had polarities of 47 +/- 6%. Only 2% of the soluble proteins had polarities below 40%, whereas 47% of the 19 membrane proteins had polarities below 40%. The membrane proteins with polarities below 40% could be separated from their respective membranes only by detergents or organic solvents, indicating the importance of hydrophobic forces in their interaction with other membrane components. It is concluded that the majority of "intrinsic" membrane proteins have low polarity, and that the polarity index is therefore a useful parameter for characterization of membrane proteins.

Amino Acids↗
PubMed1970

Biological membrane structure, I. The protein crystal model for membranes.

A geometric model for the arrangement of phospholipid and protein in biological membrane systems has been proposed. The essential principle underlying this model is that when membrane proteins polymerize, the points of contact between proteins are few, and cavities lined with predominantly nonpolar amino acids are formed. Phospholipid molecules become oriented with the fatty chains inserted into the cavities while the polar heads remain on the surface of the membrane. This orientation applies to both faces of the membrane continuum. All the lipid known to be present in membranes can be accommodated in this manner. The body of evidence supporting this model has been presented.

Crystallography↗
PubMed1970

Biological membrane structure. II. A detailed model for the retinal rod outer segment membrane.

A model, based on the available chemical, electron microscopic, and x-ray diffraction data, has been developed for the structure of the retinal rod outer segment membranes. The model consists of a double layer of globular protein molecules, with lipid bilayer filling the spaces between the proteins. The electron density across the membrane has been calculated and shown to be in agreement with that found by x-ray diffraction. The protein molecules "float" half submerged in a lipid field; this serves to orient them in the same way at all times relative to incident radiation in the intact retina.

Lipids↗
PubMed1970

Conformational model of active transport.

A model of active transport of monovalent cations in mitochondria is developed. The model is based on the coupling of electron transfer to the generation of a metastable protein conformation which in turn leads to the generation of an asymmetric surface charge, a membrane potential, and a redistribution of diffusible ions across the inner mitochondrial membrane. The ions at all times move spontaneously down an electrochemical potential gradient in this model so that there is no need to invoke the concept of an ion pump. It is shown that a wide variety of experimental facts can be rationalized in terms of the present model.

Adenosine Triphosphate↗