Mesoporous silicates (MPS) have an ordered pore structure with dimensions comparable to many biological molecules. They have been extensively explored as supports for proteins and enzymes in biocatalytic applications. Since their initial discovery, novel syntheses methods have led to precise control over pore size and structure, particle size, chemical composition, and stability, thus allowing the adsorption of a wide variety of biological macromolecules, such as heme proteins, lipases, antibody fragments, and proteases, into their structures. This Review discusses the application of ordered, large-pore, functionalized mesoporous silicates to immobilize proteins for biocatalysis.

Lactobacilli are a diverse group of species that occupy diverse nutrient-rich niches associated with humans, animals, plants and food. They are used widely in biotechnology and food preservation, and are being explored as therapeutics. Exploiting lactobacilli has been complicated by metabolic diversity, unclear species identity and uncertain relationships between them and other commercially important lactic acid bacteria. The capacity for biotransformations catalysed by lactobacilli is an untapped biotechnology resource. Here we report the genome sequences of 213 Lactobacillus strains and associated genera, and their encoded genetic catalogue for modifying carbohydrates and proteins. In addition, we describe broad and diverse presence of novel CRISPR-Cas immune systems in lactobacilli that may be exploited for genome editing. We rationalize the phylogenomic distribution of host interaction factors and bacteriocins that affect their natural and industrial environments, and mechanisms to withstand stress during technological processes. We present a robust phylogenomic framework of existing species and for classifying new species.

M1 protein and Protein H are surface proteins simultaneously present at the surface of certain strains of Streptococcus pyogenes, important pathogenic bacteria in humans. The present study concerns the structure, protein-binding properties and relationship between these two molecules. The gene encoding M1 protein (emm1) was found immediately upstream of the Protein H gene (sph). Both genes were preceded by a promoter region. Comparison of the sequences revealed a high degree of similarity in the signal peptides, the C repeats located in the central parts of the molecules and in the C-terminal cell-wall-attached regions, whereas the N-terminal sequences showed no significant similarity. Protein H has affinity for the Fc region of IgG antibodies. Also M1 protein, isolated from streptococcal culture supernatants or from Escherichia coli expressing emm1, was found to bind human IgGFc. When tested against polyclonal IgG from eight other mammalian species, M1 protein and Protein H both showed affinity for baboon, rabbit and pig IgG. M1 protein also reacted with guinea-pig IgG, whereas both streptococcal proteins were negative in binding experiments with rat, mouse, bovine and horse IgG. The two proteins were also tested against other members of the immunoglobulin super family: human IgM, IgA, IgD, IgE, beta 2-microglobulin, and major histocompatibility complex (MHC) class-I and class-II antigens. M1 protein showed no affinity for any of these molecules whereas Protein H reacted with MHC class-II antigens. M1 protein is known to bind albumin and fibrinogen also. The binding sites for these two plasma proteins and for IgGFc were mapped to different sites on M1 protein. Thus albumin bound to the C repeats and IgGFc to a region (S) immediately N-terminal of the C repeats. Finally, fibrinogen bound further towards the N-terminus but close to the IgGFc-binding site. On the fibrinogen molecule, fragment D was found to mediate binding to M1 protein. The IgGFc-binding region of M1 protein showed no similarity to that of Protein H. Still, competitive binding experiments demonstrated that the two streptococcal proteins bound to overlapping sites on IgGFc.

Cytochrome c and xylanase were adsorbed onto two mesoporous materials, SBA-15 (a pure silicate) and MSE (an organosilicate), with very similar physical properties but differing chemical compositions. A methodical order was developed whereby the influences of surface area, pore size, extent of order, particle size, surface potentials, isoelectric points, pH, and ionic strength on immobilization were explored. In silico studies of cytochrome c and xylanase were conducted before any immobilization experiments were carried out in order to select compatible materials and probe the interactions between the adsorbents and the mesoporous silicates. The stabilities of the mesoporous materials at different pH values and their isoelectric points and zeta potentials were determined. Electrostatic attraction dominated protein interactions with SBA-15, while weaker hydrophobic interactions are more prominent with MSE for both cytochrome c and xylanase. The ability of the immobilized protein/enzyme to withstand leaching was measured, and activity tests and thermostability experiments were conducted. Cytochrome c immobilized onto SBA-15 showed resistance to leaching and an enhanced activity compared to free protein. The immobilized cytochrome c was shown to have higher intrinsic activity but lower thermostability than free cytochrome c. From an extensive characterization of the surface properties of the silicates and proteins, we describe a systematic methodology for the adsorption of proteins onto mesoporous silicates. This approach can be utilized in the design of a solid support for any protein.

A truncated derivative of the phage endolysin LysK containing only the CHAP (cysteine-and histidinedependent amidohydrolase/peptidase) domain exhibited lytic activity against live clinical staphylococcal isolates, including methicillin-resistant Staphylococcus aureus. This is the first known report of a truncated phage lysin which retains high lytic activity against live staphylococcal cells.