Defects in The First Step of Lipoprotein Maturation Underlie The Synthetic Lethality of Lacking The Inner Membrane Proteins YciB And DcrB.

Nearly a quarter of the genome encodes for inner membrane proteins of which approximately a third have unassigned or poorly understood function. We had previously demonstrated that the synergy between the functional roles of the inner membrane-spanning YciB and the inner membrane lipoprotein DcrB, is essential in maintaining cell envelope integrity. In cells, the abundant outer membrane lipoprotein, Lpp, mislocalizes to the inner membrane where it forms toxic linkages to peptidoglycan.

A synergistic role for two predicted inner membrane proteins of Escherichia coli in cell envelope integrity.

The bacterial cytoplasmic membrane is a principal site of protein translocation, lipid and peptidoglycan biogenesis, signal transduction, transporters and energy generating components of the respiratory chain. Although 25-30% of bacterial proteomes consist of membrane proteins, a comprehensive understanding of their influence on fundamental cellular processes is incomplete. Here, we show that YciB and DcrB, two small cytoplasmic membrane proteins of previously unknown functions, play an essential synergistic role in maintaining cell envelope integrity of Escherichia coli.

ClpXP and ClpAP control the Escherichia coli division protein ZapC by proteolysis.

The bacterial FtsZ-ring is an essential cytokinetic structure under tight spatiotemporal regulation. In Escherichia coli, FtsZ polymerization and assembly into the Z-ring is controlled on multiple levels through interactions with positive and negative regulators. Among these regulatory factors are ZapC, a Z-ring stabilizer, and the conserved protease ClpXP, which has been shown to degrade FtsZ protofilaments in preference to FtsZ monomers.

Structural and Functional Analyses Reveal Insights into the Molecular Properties of the Escherichia coli Z Ring Stabilizing Protein, ZapC.

In Escherichia coli cell division is driven by the tubulin-like GTPase, FtsZ, which forms the cytokinetic Z-ring. The Z-ring serves as a dynamic platform for the assembly of the multiprotein divisome, which catalyzes membrane cleavage to create equal daughter cells. Several proteins effect FtsZ assembly, thereby providing spatiotemporal control over cell division.

Computational analysis of residue contributions to coiled-coil topology.

A variety of features are thought to contribute to the oligomeric and topological specificity of coiled coils. In previous work, we examined the determinants of oligomeric state. Here, we examine the energetic basis for the tendency of six coiled-coil peptides to align their α-helices in antiparallel orientation using molecular dynamics simulations with implicit solvation (EEF1.

Computational studies of colicin insertion into membranes: the closed state.

Colicins are water-soluble toxins that, upon interaction with membranes, undergo a conformational change, insert, and form pores in them. Pore formation activity is localized in a bundle of 10 α-helices named the pore-forming domain (PFD). There is evidence that colicins attach to the membrane via a hydrophobic hairpin embedded in the core of the PFD.

Negative staining and cryo-negative staining of macromolecules and viruses for TEM.

In this review we cover the technical background to negative staining of biomolecules and viruses, and then expand upon the different possibilities and limitations. Topics range from conventional air-dry negative staining of samples adsorbed to carbon support films, the variant termed the "negative staining-carbon film" technique and negative staining of samples spread across the holes of holey-carbon support films, to a consideration of dynamic/time-dependent negative staining. For each of these approaches examples of attainable data are given.

Energetic determinants of oligomeric state specificity in coiled coils.

The coiled coil is one of the simplest and best-studied protein structural motifs, consisting of two to five helices wound around each other. Empirical rules have been established on the tendency of different core sequences to form a certain oligomeric state but the physical forces behind this specificity are unclear. In this work, we model four sequences onto the structures of dimeric, trimeric, tetrameric, and pentameric coiled coils.

Modulation of the expression of p16INK4a and p14ARF by hnRNP A1 and A2 RNA binding proteins: implications for cellular senescence.

Cellular senescence is a terminal growth phase characteristic of normal human diploid fibroblasts. Altered gene expression during cellular senescence is numerous compared to that of younger proliferative cells in culture. We have previously reported that the levels and activities of hnRNP A1 and A2 RNA binding proteins are decreased in senescent human fibroblasts.

Two-dimensional model of phase segregation in liquid binary mixtures.

The hydrodynamic effects on the late stage kinetics of phase separation in liquid mixtures is studied using the model H. Mass and momentum transport are coupled via a nonequilibrium body force, which is proportional to the Peclet number alpha, i.e.

Diffusiophoresis of two-dimensional liquid droplets in a phase-separating system.

The motion of phase-separating liquid drops was simulated in two dimensions following the model H, where convection and diffusion are coupled via a body force, expressing the tendency of demixing systems to minimize their free energy. This driving force depends on the capillary number, i.e.

The circadian rhythm in intraocular pressure and its relation to diurnal ocular growth changes in chicks.

Recent investigations have shown that growing chicken eyes elongate during the day and shorten during the night. We asked whether the chick, like a number of other animals, exhibits a rhythm in intraocular pressure (IOP) and whether this rhythm might be associated with this rhythm in elongation. We find that the intraocular pressure in normal eyes is high during the day and low in the middle of the night, similar to the rhythm in ocular elongation.

Visual influences on diurnal rhythms in ocular length and choroidal thickness in chick eyes.

Recent investigations have raised the possibility that ocular diurnal rhythms might be involved in the regulation of eye growth. Specifically, the chick eye elongates with a daily rhythm, said to be absent in form-deprived eyes. The present study asks: (1) Which components of the eye have daily rhythms-only the overall eye size, or also choroidal thickness or anterior chamber depth? (2) Does the phase or amplitude of these rhythms differ in eyes growing either faster than normal (form-deprived eyes) or slower than normal (eyes recovering from form-deprivation myopia)? Using high-frequency A-scan ultrasonography that allowed fine (8-20 micron) resolution of anterior chamber depth, vitreous chamber depth, choroidal thickness and axial length, we measured normal eyes, form-deprived eyes and eyes recovering from form-deprivation myopia at 6 hour intervals for 5 days and 4 nights.