Search

This study examined the microbicidal activity of 222-nm UV radiation (UV(222)), which is potentially a safer alternative to the 254-nm UV radiation (UV(254)) that is often used for surface decontamination. Spores and/or growing and stationary-phase cells of Bacillus cereus, Bacillus subtilis, Bacillus thuringiensis, Staphylococcus aureus, and Clostridioides difficile and a herpesvirus were all killed or inactivated by UV(222) and at lower fluences than with UV(254). B. subtilis spores and cells lacking the major DNA repair protein RecA were more sensitive to UV(222), as were spores lacking their DNA-protective proteins, the α/β-type small, acid-soluble spore proteins. The spore cores’ large amount of Ca(2+)-dipicolinic acid (∼25% of the core dry weight) also protected B. subtilis and C. difficile spores against UV(222), while spores’ proteinaceous coat may have given some slight protection against UV(222). Survivors among B. subtilis spores treated with UV(222) acquired a large number of mutations, and this radiation generated known mutagenic photoproducts in spore and cell DNA, primarily cyclobutane-type pyrimidine dimers in growing cells and an α-thyminyl-thymine adduct termed the spore photoproduct (SP) in spores. Notably, the loss of a key SP repair protein markedly decreased spore UV(222) resistance. UV(222)-treated B. subtilis spores germinated relatively normally, and the generation of colonies from these germinated spores was not salt sensitive. The latter two findings suggest that UV(222) does not kill spores by general protein damage, and thus, the new results are consistent with the notion that DNA damage is responsible for the killing of spores and cells by UV(222). IMPORTANCE Spores of a variety of bacteria are resistant to common decontamination agents, and many of them are major causes of food spoilage and some serious human diseases, including anthrax caused by spores of Bacillus anthracis. Consequently, there is an ongoing need for efficient methods for spore eradication, in particular methods that have minimal deleterious effects on people or the environment. UV radiation at 254 nm (UV(254)) is sporicidal and commonly used for surface decontamination but can cause deleterious effects in humans. Recent work, however, suggests that 222-nm UV (UV(222)) may be less harmful to people than UV(254) yet may still kill bacteria and at lower fluences than UV(254). The present work has identified the damage by UV(222) that leads to the killing of growing cells and spores of some bacteria, many of which are human pathogens, and UV(222) also inactivates a herpesvirus.

The proton-driven ATP synthase (FoF1) is comprised of two rotary, stepping motors (Fo and F1) coupled by an elastic power transmission. The elastic compliance resides in the rotor module that includes the membrane-embedded FO c-ring. Proton transport by FO is firmly coupled to the rotation of the c-ring relative to other FO subunits (ab2). It drives ATP synthesis. We used a computational method to investigate the contribution of the c-ring to the total elastic compliance. We performed principal component analysis of conformational ensembles built using distance constraints from the bovine mitochondrial c-ring X-ray structure. Angular rotary twist, the dominant ring motion, was estimated to show that the c-ring accounted in part for the measured compliance. Ring rotation was entrained to rotation of the external helix within each hairpin-shaped c-subunit in the ring. Ensembles of monomer and dimers extracted from complete c-rings showed that the coupling between collective ring and the individual subunit motions was independent of the size of the c-ring which varies between organisms. Molecular determinants were identified by covariance analysis of residue co-evolution and a structural alphabet based local dynamics correlations. The residue co-evolution gave a read-out of subunit architecture. The dynamic couplings revealed that the hinge for both ring and subunit helix rotations was constructed from the proton-binding site and the adjacent glycine motif (IB-GGGG) in the mid-membrane plane. IB-GGGG motifs were linked by long-range couplings across the ring, while intra-subunit couplings connected the motif to the conserved cytoplasmic loop and adjacent segments. The correlation with principal collective motions shows that the couplings underlie both ring rotary and bending motions. Non-contact couplings between IB-GGGG motifs matched the co-evolution signal as well as contact couplings. The residue co-evolution reflects the physiological importance of the dynamics that may link proton transfer to ring compliance.

In female (XX) mammals, one of the two X chromosomes is inactivated to ensure an equal dose of X-linked genes with males (XY). X-chromosome inactivation in eutherian mammals is mediated by the non-coding RNA Xist. Xist is not found in metatherians (marsupials), and how X-chromosome inactivation is initiated in these mammals has been the subject of speculation for decades. Using the marsupial Monodelphis domestica, here we identify Rsx (RNA-on-the-silent X), an RNA that has properties consistent with a role in X-chromosome inactivation. Rsx is a large, repeat-rich RNA that is expressed only in females and is transcribed from, and coats, the inactive X chromosome. In female germ cells, in which both X chromosomes are active, Rsx is silenced, linking Rsx expression to X-chromosome inactivation and reactivation. Integration of an Rsx transgene on an autosome in mouse embryonic stem cells leads to gene silencing in cis. Our findings permit comparative studies of X-chromosome inactivation in mammals and pose questions about the mechanisms by which X-chromosome inactivation is achieved in eutherians.

An abstract representation, similar to a Periodic Table, was used to generate a large number of idealised protein folds. Each of these was taken as a framework onto which a variety of predicted secondary structures were mapped and the resulting models constructed at a more detailed level. The best of these were refined and rescored. On a set of five proteins, the correct fold was scored highly in each with the top models having a low root-mean-square deviation from the known structure.

The specificity determinants for susceptibility to resistance by the Fv1 n and b alleles map to amino acid 110 of the murine leukemia virus CA protein. To study the interaction between Fv1 and CA, we examined changes in CA resulting in the loss of susceptibility to Fv1 resistance in naturally occurring NB- and NR-tropic viruses. A variety of amino acid changes affecting Fv1 tropism were identified, at CA positions 82, 92 to 95, 105, 114, and 117, and they all were mapped to the apparent exterior of virion-associated CA. These amino acids may form a binding surface for Fv1.

Calcium and phospholipid binding proteins have been identified and localized by immunocytochemistry in a wide range of cells and tissues. Two of these proteins (calpactins) also bind F-actin and are substrates for tyrosine kinases. The similar membrane-binding properties of these molecules arise from conserved amino acid sequences and a model is proposed for the tertiary structure of a common calcium and phospholipid binding domain.

Greenberg, M. E. & Edelman, G. M. (1983) Cell 33. 767-779 Hexham. J. M., Totty. N. F., Waterfield, M. D. & Crumpton, M. J. (1986) Bioclwrn. Biophys. Res. Cornmun. 134, 248 -254 Huang. K. S., Wallner, B. P., Mattaliano, R. J., Tizard, R., Burne, L.. Frey, A,. Hession, C., McGray, P., Sinclair, L. K., Chow, E. P., Browning, J. L., Ramachandran, K. L.. Tang, J., Smart, J . E. & Pepinsky, R. B. (1986) CeN46, 191-199 82. 78847888