Nucleoporin‐like polypeptide (NLP) hydrogels are developed by mimicking nucleoporins, proteins that form gel filters regulating transport into the nucleus. Using protein polymers of a minimal consensus repeat, the NLPs selectively enhance transport of cargo–carrier complexes similar to the natural nuclear pore system. The engineered protein gels additionally have tunable mechanical and transport properties and can be biosynthesized at high yield, making them promising materials for advanced separation technologies.

INTRODUCTORY PARAGRAPH Mucus barriers accommodate trillions of microbes throughout the human body while preventing pathogenic colonization. 1 In the oral cavity, saliva containing the mucins MUC5B and MUC7 forms a pellicle that coats the soft tissue and teeth to prevent infection by oral pathogens, such as Streptococcus mutans . 2 Salivary mucin can interact directly with microbes through selective agglutinin activity and bacterial binding, 2 – 4 but the extent and basis of saliva’s protective functions are not well understood. Using an ex vivo saliva model, we identify MUC5B as an inhibitor of microbial virulence. Specifically, we find natively purified MUC5B downregulates the expression of quorum sensing pathways activated by the competence stimulating peptide (CSP) and the sigX inducing peptide (XIP). 5 Further, MUC5B prevents the acquisition of antimicrobial resistance through natural genetic transformation, a process activated through quorum sensing. Our data reveal the effect of MUC5B is mediated by its associated glycans, which are potent suppressors of quorum sensing and genetic transformation, even when removed from the mucin backbone. Together, these results present mucin glycans as a host strategy for domesticating potentially pathogenic microbes without killing.

The nuclear pore complex controls the passage of molecules via hydrophobic phenylalanine-glycine (FG) domains on nucleoporins. Such FG domains consist of repeating units of FxFG, FG, or GLFG sequences, many of which are interspersed with highly charged amino acid sequences. Despite the high density of charge in certain FG domains, if and how charge influences FG-domain self-assembly and selective binding of nuclear transport receptors is largely unexplored. Using rationally designed short peptide sequences, we determined that the charge type and identity of amino acids surrounding FG sequences impact the structure and selectivity of FG-based gels. Moreover, we showed that spatial localization of the charged amino acids with respect to the FG sequence determines the degree to which charge influences hydrophobic interactions. Taken together, our study highlights that charge type and placement of amino acids regulate FG-sequence function and are important considerations when studying the mechanism of nuclear pore complex transport in vivo.

c Numerous bacteria assemble proteinaceous microcompartments to isolate certain biochemical reactions within the cytoplasm. The assembly, structure, contents, and functions of these microcompartments are active areas of research. Here we show that the Gram-negative sporulating bacterium Acetonema longum synthesizes propanediol utilization (PDU) microcompartments when starved or grown on 1,2-propanediol (1,2-PD) or rhamnose. Electron cryotomography of intact cells revealed that PDU microcompartments are highly irregular in shape and size, similar to purified PDU microcompartments from Salmonella enterica serovar Typhimurium LT2 that were imaged previously. Homology searches identified a 20-gene operon in A. longum that contains most of the structural, enzymatic, and regulatory genes thought to be involved in PDU microcompartment assembly and function. Transcriptional data on PduU and PduC, which are major structural and enzymatic proteins, respectively, as well as imaging, indicate that PDU microcompartment synthesis is induced within 24 h of growth on 1,2-PD and after 48 h of growth on rhamnose. Bacterial microcompartments are small, cytoplasmic, organelle-like bodies consisting of a thin, selectively permeable proteinaceous shell that surrounds a cluster of enzymes. Together, these isolate certain metabolic pathways away from the rest of the cytoplasm. Microcompartments may increase metabolic efficiency by concentrating enzymes and substrates, inhibiting nonproductive side reactions, or sequestering toxic by-products (1, 2). The best-studied microcompartments are the "carboxysomes" that sequester ribulose 1,5-bisphosphate carboxylase/oxygenase (RubisCO) and facilitate carbon fixation (3, 4). After early electron microscopy images of carboxysomes revealed their general size and shape (5), crystal structures of the shell proteins led to pseudoatomic models of carboxysomes as irregular polyhedra with hexagonally packed faces joined at the vertices by pentagonal disclinations (6, 7). In the case of carboxysomes, it was also recently shown that the RubisCO enzymes destined to be internalized cluster together and then nucleate the assembly of the shell (8). Electron cryotomography (ECT) (9) of purified carboxysomes (10) and then of intact cells producing carboxysomes (11) has shown that while purification enriches for more-nearly-icosahedral shapes, carboxysomes inside cells are more heterogeneous, exhibit ordered layers of enzymes packed against the shell, and harbor small internal storage granules as well as elaborate connections to larger, external storage granules (11).In addition to carboxysomes, there are several other types of bacterial microcompartments, including propanediol utilization (PDU) and ethanolamine microcompartments (12, 13). Whether or not all microcompartments share similar assembly and structural features remains unclear. Projection images of plastic-embedded sections of PDU and ethanolamine microcompartments from Salmonella enterica and Lactobacillus reuteri have shown that these are also irre...