Fort CnoX: Protecting Bacterial Proteins From Misfolding and Oxidative Damage

How proteins fold and are protected from stress-induced aggregation is a long-standing mystery and a crucial question in biology. Here, we present the current knowledge on the chaperedoxin CnoX, a novel type of protein folding factor that combines holdase chaperone activity with a redox protective function. Focusing on Escherichia coli CnoX, we explain the essential role played by this protein under HOCl (bleach) stress, discussing how it protects its substrates from both aggregation and irreversible oxidation, which could otherwise interfere with refolding. Finally, we highlight the unique ability of CnoX, apparently conserved during evolution, to cooperate with the GroEL/ES folding machinery.

FPGA implementation of folded FIR filter architecture with changeable folding factor

The application of folding technique to the bit-plane systolic FIR filter architecture that enables the implementation of changeable folding factor on to the fixed size array is described in this paper. The bit-level transformation of the original data flow graph (DFG), for the bit-plane architecture, that provides the successful application of the folding technique with changeable folding is presented at transfer function level The mathematical path that describes the transformation is given, and implications at the DFG level are discussed. Changeable folding sets are involved with aim to increase the throughput of the folded system reducing the folding factor according to the coefficient length. The folded FIR filter architecture is described in VHDL as a parameterized FIR filtering core and implemented in FPGA technology. The design "tradeoffs" relating on the occupation of the chip resources and achieved throughputs are presented.

Intragenic Suppressors of an OmpF Assembly Mutant and Assessment of the Roles of Various OmpF Residues in Assembly through Informational Suppressors

ABSTRACT We employed two separate genetic approaches to examine the roles of various OmpF residues in assembly. In one approach, intragenic suppressors of a temperature-sensitive OmpF assembly mutant carrying a W214E substitution were sought at 42°C, or at 37°C in a genetic background lacking the periplasmic folding factor SurA. In the majority of cases (58 out of 61 revertants), the suppressors mapped either at the original site (position 214) or two residues downstream from it. In the remaining three revertants that were obtained in asurA background, an alteration of N230Y was located 16 residues away from the original site. The N230Y suppressor also corrected OmpF315 assembly at 42°C in asurA + background, indicating that the two different physiological environments imposed similar assembly constraints. The specificity of N230Y was tested against five different residues at position 214 of mature OmpF. Clear specificity was displayed, with maximum suppression observed for the original substitution at position 214 (E214) against which the N230Y suppressor was isolated, and no negative effect on OmpF assembly was noted when the wild-type W214 residue was present. The mechanism of suppression may involve compensation for a specific conformational defect. The second approach involved the application of informational suppressors (Su-tRNA) in combination with ompF amber mutations to generate variant OmpF proteins. In this approach we targeted the Y40, Q66, W214, and Y231 residues of mature OmpF and replaced them with S, Q, L, and Y through the action of Su-tRNAs. Thus, a total of 16 variant OmpF proteins were generated, of which three were identical to the parental protein, and two variants carrying W214Q and Y231Q substitutions were similar to assembly-defective proteins isolated previously (R. Misra, J. Bacteriol. 175:5049–5056, 1993). The results obtained from these analyses provided useful information regarding the compatibility of various alterations in OmpF assembly.

Reduction in myotendinous junction surface area of rats subjected to 4-day spaceflight

The surface area of myotendinous junctions (MTJs), expressed relative to the cross-sectional area of myofibrils attached to them, was determined using established morphometric techniques in which the digitlike processes of the cell at MTJs are modeled as circular paraboloids. The relative area, called the folding factor, was measured for six rats after a 4-day spaceflight and six control rats maintained in a vivarium under otherwise identical conditions. Spaceflight resulted in a significant reduction in relative MTJ surface area, from 19.7 +/- 2.3 (SD) in control animals to 13.3 +/- 2.5 for animals after spaceflight. Furthermore, space animals displayed increased numbers of fibroblasts enriched in rough endoplasmic reticulum near the MTJ, a greater number of ribosomes and mitochondria within muscle at the MTJ, and increased occurrence of lesions in the connective tissue near the MTJ. The results indicate that spaceflight, possibly through the removal of gravity-associated loading from muscle, causes a modification in MTJ structure and may result in injuries at MTJs after return to normal loading.