Calcium ion and muscle contraction.

Teichoic acids (TAs) are major wall and membrane components of most gram-positive bacteria. With few exceptions, they are polymers of glycerol-phosphate or ribitol-phosphate to which are attached glycosyl and d-alanyl ester residues. Wall TA is attached to peptidoglycan via a linkage unit, whereas lipoteichoic acid is attached to glycolipid intercalated in the membrane. Together with peptidoglycan, these polymers make up a polyanionic matrix that functions in (i) cation homeostasis; (ii) trafficking of ions, nutrients, proteins, and antibiotics; (iii) regulation of autolysins; and (iv) presentation of envelope proteins. The esterification of TAs with d-alanyl esters provides a means of modulating the net anionic charge, determining the cationic binding capacity, and displaying cations in the wall. This review addresses the structures and functions of d-alanyl-TAs, the d-alanylation system encoded by the dlt operon, and the roles of TAs in cell growth. The importance of dlt in the physiology of many organisms is illustrated by the variety of mutant phenotypes. In addition, advances in our understanding of d-alanyl ester function in virulence and host-mediated responses have been made possible through targeted mutagenesis of dlt. Studies of the mechanism of d-alanylation have identified two potential targets of antibacterial action and provided possible screening reactions for designing novel agents targeted to d-alanyl-TA synthesis.

A Continuum of Anionic Charge: Structures and Functions of d-Alanyl-Teichoic Acids in Gram-Positive Bacteria

Osmolytes are small organic compounds that affect protein stability and are ubiquitous in living systems. In the equilibrium protein folding reaction, unfolded (U) ⇌ native (N), protecting osmolytes push the equilibrium toward N, whereas denaturing osmolytes push the equilibrium toward U. As yet, there is no universal molecular theory that can explain the mechanism by which osmolytes interact with the protein to affect protein stability. Here, we lay the groundwork for such a theory, starting with a key observation: the transfer free energy of protein backbone from water to a water/osmolyte solution, Δgtr, is negatively correlated with an osmolyte’s fractional polar surface area. Δgtr measures the degree to which an osmolyte stabilizes a protein. Consequently, a straightforward interpretation of this correlation implies that the interaction between the protein backbone and osmolyte polar groups is more favorable than the corresponding interaction with nonpolar groups. Such an interpretation immediately suggests the existence of a universal mechanism involving osmolyte, backbone, and water. We test this idea by using it to construct a quantitative solvation model in which backbone/solvent interaction energy is a function of interactant polarity, and the number of energetically equivalent ways of realizing a given interaction is a function of interactant surface area. Using this model, calculated Δgtr values show a strong correlation with measured values (R = 0.99). In addition, the model correctly predicts that protecting/denaturing osmolytes will be preferentially excluded/accumulated around the protein backbone. Taken together, these model-based results rationalize the dominant interactions observed in experimental studies of osmolyte-induced protein stabilization and denaturation.

https://www.pnas.org/content/pnas/103/38/13997.full.pdf

A molecular mechanism for osmolyte-induced protein stability

http://archive.gersteinlab.org/papers/e-print/volfold-structure/text.pdf

Volume changes on protein folding.

http://archive.gersteinlab.org/papers/e-print/std-vols-jmb/std-vols-jmb.pdf

The packing density in proteins: standard radii and volumes.

THE misfortunes of war have rendered this impressive book, published in 1943, inaccessible in Britain until recent months. No shorter description is possible than to say it is worthy of those great men to whom it is dedicated, Bate Hardy, Loeb, Osborne and Sorensen. Proteins, Amino-Acids and Peptides as Ions and Dipolar Ions Edwin J. Cohn John T. Edsall, with chapters by John G. Kirkwood, Hans Mueller, J. L. Oncley and George Scatchard. Pp. xviii + 686. American Chemical Society Monograph Series. (New York: Reinhold Publishing Corporation, 1943.) 13.50 dollars.

Proteins, Amino-Acids and Peptides as Ions and Dipolar Ions

AN unusual protein of fibrous character has been isolated from the fibrillar fraction of skeletal and cardiac muscle. It is simply prepared by washing away the sarcoplasmic components of finely minced muscle and dehydrating the residue in ethanol and then in ether. The debris, consisting mainly of stroma protein and of myosin denatured in situ, is soaked in a molar solution of potassium chloride at pH 7, when a clear viscous extract is obtained containing tropomyosin and other proteins which are then precipitated at pH 4.5. After redispersal at pH 7, the contaminating proteins are largely denatured, and are almost quantitatively removed in ammonium sulphate solutions of 41 per cent saturation. The tropomyosin, precipitated between 49 and 60 per cent saturation, is filtered, dissolved, dialysed and purified by repeating the isoelectric precipitation and salting-out procedures.

Tropomyosin: a new asymmetric protein component of muscle.

/pdf/protein-structure-and-biological-activity-vsnbw61hek.pdf

Protein Structure and Biological Activity

WHEN surface tension is determined by the dropweight method, the drops must be allowed to fall as nearly as possible under the influence of gravity alone. In practice, the time of formation of a drop should be not less than five minutes1.

/pdf/determination-of-surface-tension-by-the-drop-weight-method-1w354siqtg.pdf

Determination of Surface Tension by the Drop-Weight Method

ALTHOUGH it is well known that liquids may be supersaturated with gases, the extent to which a gas may be retained in supersaturated solution does not seem to be generally realised, and no quantitative information about the phenomenon is given in most textbooks on physical chemistry.

Kenneth C. Bailey

Papers

Proteins, Amino-Acids and Peptides as Ions and Dipolar Ions

Tropomyosin: a new asymmetric protein component of muscle.

Protein Structure and Biological Activity

Determination of Surface Tension by the Drop-Weight Method

Supersaturation of Liquids with Gases