Structural and Functional Properties of Staphylococcal Superantigen-Like Protein 4

ABSTRACTStaphylococcus aureusis a prevalent and significant human pathogen. Among the repertoire of virulence factors produced by this bacterium are the 14 staphylococcal superantigen-like (SSL) proteins. SSL protein 4 (SSL4) is one member of this family and contains a highly conserved carbohydrate binding site also found in SSL2, SSL3, SSL5, SSL6, and SSL11. Recombinant SSL4t, comprising amino acids 109 to 309 of Newman strain SSL4 (SSL4-Newman), has been shown to bind and be internalized by human granulocytes and macrophages in a sialic-acid (Sia)-dependent manner. SSL4tcan compete with itself for cell binding, indicating that binding is target specific. A 2.5-Å-resolution crystal structure of SSL4tcomplexed with sialyl Lewis X (sLex) [sLex-Neu5Acα2-3Galβ1-4(Fucα1-3)GlcNAc] revealed a similar binding site to SSL5 and SSL11. These data, along with data on SSL4tbinding to a glycan array and biosensor analysis of sLexand sialyllactosamine (sLacNac) binding are compared with those for SSL11. Although these proteins show great similarity in their carbohydrate binding sites, with a root mean square (RMS) difference between main chain atom positions of only 0.34 Å, these proteins differ in detail in their affinity for sLexand sLacNac, as well as their glycan preference. Together with cell binding data, this shows howS. aureusproduces multiple related proteins that target myeloid cells through specific sialyllactosamine-containing glycoproteins.

Protein structures and complexes: what they reveal about the interactions that stabilize them

The rapid increase in the number of high-quality protein structures provides an expanding knowledge resource about interactions involved in stabilizing protein three-dimensional structures and the complexes they form with other molecules. In this paper we first review the results of some recent analyses of protein structure, including restrictions on local conformation, and a study of the geometry of hydrogen bonds. Then we consider how such empirical data can be used as a test bed for energy calculations, by using the observed spatial distributions of side chain/atom interactions to assess three different methods for modelling atomic interactions in proteins. We have also derived a new empirical solvation potential which aims to reproduce the hydrophobic effect. To conclude we address the problem of molecular recognition and consider what we can deduce about the interactions involved in the binding of peptides to proteins.

Unusually high values of the quotient d ln η/d ln M of some low-molecular-weight liquid polymers

Unusually high values of the quotient d ln η/d ln M ≡ a (where η is viscosity and M is molecular weight) found for some low-molecular-weight liquid polymers (4 ⪬ a ⪬ 8) are discussed in terms of the theory of flow processes of polymeric liquids. The effect is assigned mainly to the dependence on the chain length of the friction factor per main chain atom or atomic group but deviations of short chains from the conformation of random coils can also contribute significantly. The variation of the quotient a with temperature, however, is due to the former factor only.

Practical Evaluation of the [η]-M Relationship II. Estimation of Kθ Values of Polymer Solutions

A method is proposed for the prediction of the intrinsic viscosity of θ-solutions, based on the constitution of the dissolved polymer. The method makes use of additive values for constitutional groups to calculate a quantity that represents the specific chain stiffness per main chain atom.

Viscosity—Molecular Weight Relations for Various Synthetic Rubbers

Measurements of six different high polymers have shown that the intrinsic viscosity of the solutions depends on approximately the two-thirds power of the molecular weight. Dependence of the viscosity on the weight per chain atom of the polymer is indicated.