We demonstrate the presence of a symbiotic stability reinforcement effect between bioentities and crystalline ZIFs, where the ZIF protects biomolecules from denaturation and the biomolecules improve the acid resistance of the ZIF framework. The strategy provides a potential route for stabilizing MOFs for diverse technological and industrial applications.

Tailed DNA bacteriophages assemble empty procapsids that are subsequently filled with the viral genome by means of a DNA packaging machine situated at a special fivefold vertex. The packaging machine consists of a "small terminase" and a "large terminase" component. One of the functions of the small terminase is to initiate packaging of the viral genome, whereas the large terminase is responsible for the ATP-powered translocation of DNA. The small terminase subunit has three domains, an N-terminal DNA-binding domain, a central oligomerization domain, and a C-terminal domain for interacting with the large terminase. Here we report structures of the central domain in two different oligomerization states for a small terminase from the T4 family of phages. In addition, we report biochemical studies that establish the function for each of the small terminase domains. On the basis of the structural and biochemical information, we propose a model for DNA packaging initiation.T4-like phages | X-ray crystal structure M ost tailed bacteriophages and some eukaryotic viruses employ a molecular motor to package their genomic DNA into preformed empty capsids (procapsids or proheads) (1-3). A large amount of negatively charged DNA is packaged into the confined space within the capsid to near crystalline density, creating a pressure of about 60 atm inside the head (4). To counteract the increasing pressure during DNA packaging, the motor needs to generate forces of up to 60 pN (4-6), which is about 20 times the force generated by myosin motors. The energy for genome packaging is provided by ATP hydrolysis.Generally, DNA packaging machines consist of three components (3, 7). The first component is a dodecameric portal protein located at the special fivefold vertex of the capsid through which the DNA is threaded into the head. Crystal structures of portal proteins from phages φ29 (8), SPP1 (9), and P22 (10) show that they form cone-shaped structures with a central cylindrical channel about 36 Å wide. Cryoelectron microscopy (cryo-EM) studies of phages φ29 (8), SPP1 (11), T4 (12), P22 (13,14), and ϵ15 (15) show that the wider end of the cone-shaped portal is inside the capsid, and the narrower end protrudes out of the capsid. The portal provides a site of attachment for the DNA packaging motor to the procapsid and for the tail to the filled capsid. To what extent the portal participates in DNA packaging is not clear, but it might act as a valve to stop the DNA from escaping the head during successive strokes of the packaging motor (16) and when completely packaged (17). It was also proposed that the portal might be involved in sensing when the head is fully packaged (18,19).The second component of the DNA packaging machine is the large "terminase" motor protein which has both an ATPase activity to provide energy for packaging and a nuclease activity for packaging initiation and termination (20). In most DNA phages, the newly replicated genome is a branched concatemer without any accessible free ends (3). It needs to be cleaved in ...

The structure and assembly of bacteriophage T4 has been extensively studied. However, the detailed structure of the portal protein remained unknown. Here we report the structure of the bacteriophage T4 portal assembly, gene product 20 (gp20), determined by cryo-electron microscopy (cryo-EM) to 3.6 Å resolution. In addition, analysis of a 10 Å resolution cryo-EM map of an empty prolate T4 head shows how the dodecameric portal assembly interacts with the capsid protein gp23 at the special pentameric vertex. The gp20 structure also verifies that the portal assembly is required for initiating head assembly, for attachment of the packaging motor, and for participation in DNA packaging. Comparison of the Myoviridae T4 portal structure with the known portal structures of φ29, SPP1 and P22, representing Podo- and Siphoviridae, shows that the portal structure probably dates back to a time when self-replicating microorganisms were being established on Earth.

Metal-organic frameworks (MOFs) have recently emerged as excellent hosting matrices for enzyme immobilization, offering superior physical and chemical protection for biocatalytic reactions.However,for multienzyme and cofactordependent biocatalysis,the subtle orchestration of enzymes and cofactors is largely disrupted upon immobilizing in the rigid crystalline MOF network, whichl eads to am uchr educed biocatalytic efficiency.H erein, we constructed hierarchically porous MOFs by controlled structural etching to enhance multienzyme and cofactor-dependent enzyme biocatalysis.The expanded sizeo ft he pores can provide sufficient space for accommodated enzymes to reorientate and spread within MOFs in their lower surface energy state as well as to decrease the inherent barriers to accelerate the diffusion rate of reactants and intermediates.M oreover,t he developed hierarchically porous MOFs demonstrated outstanding tolerance to inhospitable surroundings and recyclability.

Summary -While catabolism of amino acids is believed to play an important role in cheese f1avor development, the pathways present in cheese microflora are poorly understood. To determine the pathways of aromatic amino acid catabolism in lactococci and effects of Cheddar cheese ripening conditions on catabolic enzymes and products, eight starter lactococcal strains were screened. Cell-free extracts prepared from these strains were found to contain an oe-ketoglutarate-dependent aminotransferase activity with tryptophan, tyrosine and phenylalanine. Tryptophan, tyrosine and phenylalanine aminotransferase specifie activities (Il mol product formed/mg proteinlmin) ranged from 0.30 to 2.8 10-3 , 0.93 to 7.3 10-3 and 1.5 to 7.2 10-3 , respectively. Metabolites produced from tryptophan by a cellfree extract of Lactococcus lactis S3 were indolepyruvic acid, indoleacetic acid and indole-3-aldehyde. Indoleacetic acid and indole-3-aldehyde can form spontaneously from indolepyruvic acid under the conditions employed. A defined medium was used to determine whether the aminotransferase(s) was expressed and which metabolite(s) accumulate under conditions that simulated those of ripening Cheddar cheese in terms of pH, salt, temperature and carbohydrate starvation. The results indicated that the aminotransferase(s) was expressed and stable under these conditions. The tryptophan metabolites that accumulated were determined to be strain-specific. lactococcus / aminotransferase / aromatic amino acid / catabolism / cheese flavor Résumé -Catabolisme des acides aminés aromatiques des lactocoques. Alors que le catabolisme des acides aminés est perçu comme jouant un rôle important dans le développement de la flaveur du fromage; les voies métaboliques liées à la microflore du fromage ne sont que très partiellement éta-blies. Pour déterminer les voies du catabolisme des acides aminés aromatiques dans les lactocoques, et les effets des conditions d'affinage du Cheddar sur les enzymes cataboliques et sur les produits, huit souches de levains lactocoques on été analysées. Des extraits de cellules préparées à partir de ces souches possédaient une activité aminotransférase oe-ketoglutarate dépendante du tryptophane, de la tyrosine et de la phénylalanine. Les activités aminotransférases spécifiques du tryptophane, de la * Oral communication at the IDF Symposium 'Ripening and Quality of Cheeses',

Synthetic nano/micromotors are a burgeoning class of materials with vast promise for applications ranging from environmental remediation to nanomedicine. Motility of these motors is generally controlled by the concentration of accessible fuel, and therefore engineering speed-regulation mechanism, particularly using biological triggers, remains a continuing challenge. Here we demonstrate control over the movement of super-assembled porous framework micromotors (SAFMs) via a reversible, biological-relevant pH-responsive regulatory mechanism. Succinylated β-lactoglobulin and catalase were super-assembled in porous framework particles, where the β-lactoglobulin is permeable at neutral pH. This permeability allows the fuel (H 2 O 2 ) to access catalase leading to autonomous movement of the micromotors. However, at mild acidic pH, succinylated β-lactoglobulin undergoes a reversible gelation process preventing the access of fuel into the micromotors where the catalase resides. To our knowledge this study represents the first example of chemically driven motors with rapid, reversible pH-responsive motility. Furthermore, the porous framework significantly enhances the biocatalytic activity of catalase, allowing ultralow H 2 O 2 concentrations to be exploited at physiological conditions. We envision that the simultaneous exploitation of pH and chemical potential of such nanosystems could have potential applications as stimulus-responsive drug delivery vehicles to take the benefit from the complex biological environment.Received: ((will be filled in by the editorial staff))Revised: ((will be filled in by the editorial staff))

Geometric or electronic confinement of guests inside nanoporous hosts promises to deliver unusual catalytic or opto-electronic functionality from existing materials but is challenging to obtain particularly using metastable hosts, such as metal–organic frameworks (MOFs). Reagents (e.g. precursor) may be too large for impregnation and synthesis conditions may also destroy the hosts. Here we use thermodynamic Pourbaix diagrams (favorable redox and pH conditions) to describe a general method for metal-compound guest synthesis by rationally selecting reaction agents and conditions. Specifically we demonstrate a MOF-confined RuO2 catalyst (RuO2@MOF-808-P) with exceptionally high catalytic CO oxidation below 150 °C as compared to the conventionally made SiO2-supported RuO2 (RuO2/SiO2). This can be caused by weaker interactions between CO/O and the MOF-encapsulated RuO2 surface thus avoiding adsorption-induced catalytic surface passivation. We further describe applications of the Pourbaix-enabled guest synthesis (PEGS) strategy with tutorial examples for the general synthesis of arbitrary guests (e.g. metals, oxides, hydroxides, sulfides).

Pathway optimization plays an important role in fine-tuning metabolic pathways. In most conditions, more than three genes are involved in the biosynthesis pathway of a specific target product. To improve the titer of products, rational regulation of a group of genes by a series of promoters with different strengths is essential. On the basis of a series of RNA-Seq data, a set of 66 native promoters was chosen to fine-tune gene expression in Saccharomyces cerevisiae. Promoter strength was characterized by measuring the fluorescence strength of the enhanced green fluorescent protein through fluorescence-activated cell sorting. The expressions of PTDH1, PPGK1, PINO1, PSED1, and PCCW12 were stronger than that of PTDH3, whereas those of another 15 promoters were stronger than that of PTEF1. Then, 30 promoters were chosen to optimize the biosynthesis pathway of (2S)-naringenin from p-coumaric acid. With a high-throughput screening method, the highest titer of (2S)-naringenin in a 5 L bioreactor reached 1.21 g/L from p-coumaric acid, which is the highest titer according to the currently available reports.