The
antimetabolite pentyl pantothenamide has broad spectrum antibiotic
activity but exhibits enhanced activity against Escherichia
coli. The PanDZ complex has been proposed to regulate the
pantothenate biosynthetic pathway in E. coli by limiting
the supply of β-alanine in response to coenzyme A concentration.
We show that formation of such a complex between activated aspartate
decarboxylase (PanD) and PanZ leads to sequestration of the pyruvoyl
cofactor as a ketone hydrate and demonstrate that both PanZ overexpression-linked
β-alanine auxotrophy and pentyl pantothenamide toxicity are
due to formation of this complex. This both demonstrates that the
PanDZ complex regulates pantothenate biosynthesis in a cellular context
and validates the complex as a target for antibiotic development.
Staphylococcus aureus sortase A is a transpeptidase that has been extensively exploited for site-specific modification of proteins and was originally used to attach a labeling reagent containing an LPXTG recognition sequence to a protein or peptide with an N-terminal glycine. Sortase mutants with other recognition sequences have also been reported, but in all cases, the reversibility of the transpeptidation reaction limits the efficiency of sortase-mediated labeling reactions. For the wildtype sortase, depsipeptide substrates, in which the scissile peptide bond is replaced with an ester, allow effectively irreversible sortasemediated labeling as the alcohol byproduct is a poor competing nucleophile. In this paper, the use of depsipeptide substrates for evolved sortase variants is reported. Substrate specificities of three sortases have been investigated allowing identification of an orthogonal pair of enzymes accepting LPEToG and LPESoG depsipeptides, which have been applied to dual N-terminal labeling of a model protein mutant containing a second, latent Nterminal glycine residue. The method provides an efficient orthogonal site-specific labeling technique that further expands the biochemical protein labeling toolkit.
Hanson, NJ, Carriveau, DM, Morgan, HE, Smith, AR, Michael, TJ, and Miller, MG. Deception of ambient temperature does not elicit performance benefits during a 5 km run in hot, humid conditions. J Strength Cond Res 32(8): 2250-2257, 2018-The purpose of this study was to investigate the effect of deception of ambient temperature on 5 km performance in recreational runners. Eleven participants (6 men, 5 women) each performed three 5 km runs in a random order consisting of a control trial (CON) in temperate conditions (21° C, 43% RH), a hot humid trial (HOT; 31° C, 65% RH) and a deception trial (DEC; 31° C, 65% RH), where participants were told it was 5° C lower than it actually was. Overall completion time was recorded at the end of trials; thermal sensation (TS), rating of perceived exertion (RPE), and core temperature (TC) were recorded each kilometer. Participants completed the 5 km run faster in the CON condition (23:18 ± 2:05; mean ± SD) compared with DEC (p = 0.005) and HOT (p = 0.014). There was no difference in completion time (p = 0.554) between DEC (25:11 ± 2:41) and HOT (24:25 ± 2:47). Similarly, TS was lower in the CON condition (5.7 ± 0.2) compared with DEC and HOT (p < 0.001 and p = 0.016, respectively) and no differences were seen between the DEC (6.4 ± 0.2) and HOT (6.5 ± 0.2) conditions. No differences in RPE (p = 0.115) or rise in TC (p = 0.289) were seen between the 3 conditions. Deception of the environmental conditions did not positively affect 5 km running performance, and no differences were seen in physiological or psychological variables.
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