Antimetabolic activities of 2-fluoro-L-histidine.

2-Fluoro-L-Histidine inhibits protein synthesis in various cell cultures, as measured by ³H-leucine incorporation. This histidine analog also inhibits the cytopathogenicity of a number of RNA and DNA viruses in primary and continuous cell cultures; it blocks the transformation of normal mouse (MO) cells by murine sarcoma virus, and partially suppresses the release of murine leukemia virus by a continuously infected mouse cell line (JLSV5). In human skin fibroblasts, it reduces the interferon-inducing capacity of poly(I)·poly(C). Inhibition of cell protein synthesis may be the common cause of the various effects. 4-Fluoro-L-histidine is essentially inert in all of the test systems examined.     

Ethanol-induced cytochrome P-450: Catalytic activity after partial purification

Cytochrome P-450 was partially purified from liver microsomes obtained from control, ethanol, phenobarbital, and 3-methylcholanthrene-treated rats. Benzphetamine demethylation, benzpyrene hydroxylation and aniline hydroxylation activities were assayed in a reconstituted system using fixed amounts of reductase and lipids, and increasing amounts of cytochrome P-450 from each source. Cytochrome P-450 from ethanol-fed rats showed substrate specificity differing from cytochrome P-450 obtained from control, phenobarbital and 3-methylcholanthrene-treated rats.     

Separation of two HMM-S1 species from white muscle myosin

Heavy meromyosin subfragment 1 was resolved by chromatography on DEAE-cellulose into two fractions characterized by the nature of the alkali light chains present. It was shown that even in an HMM-S1 preparation with an extensive fragmentation of the heavy chain a polyacrylamide gel electrophoresis analysis differentiates alkali light chains among the light fragmentation components. A non-fragmented HMM-S1 was obtained from a papain digest of myofibrils and the chromatographic analysis supplied further evidence of the separation of the two species of HMM-S1 present in rabbit white muscle myosin.     

Differential inactivation of the “L” and “Ly+” amino acid transport systems by a sulfhydryl reagent and a photoaffinity probe

Using a substrate-stimulated amino acid efflux system, it has been shown that the “Ly⁺” and “L” amino acid transport systems of mouse embryo cells in culture are differentially inhibited by parachloromercuribenzene sulfonate (PCMB-S) and the photoaffinity probe 4-fluoro-3-nitrophenylazide (FNPA). Three types of evidence support the conclusion that these transport systems are mediated by separate carrier proteins. (1) The specificity of substrate-stimulated efflux is high for each system; (2) PCMB-S inhibits l-phenylalanine and l-leucine stimulated l-[³H]phenylalanine efflux with no effect on l-lysine stimulated l-[³H]lysine efflux, and (3) the photoaffinity probe FNPA inhibits l-lysine efflux with little effect on the l-phenylalanine-stimulated efflux.     

Incorporation of methionine-[methyl-2H3] and mevalonic acid-[2-14C,(4R)-4-3H1] into Phycomyces blakesleeanus sterols

Ergosterol, episterol, 4α-methyl-5α-ergosta-8,24(28)-dien-3β-ol and 24-methylene-24,25-dihydrolanosterol, isolated from Phycomyces blakesleeanus grown in the presence of methionine-[methyl-²H₃], each contained two deuterium atoms; lanosterol, however, was unlabelled. The ¹⁴C:³H atomic ratio of the following sterols isolated from P. blakesleeanus grown in the presence of mevalonic acid-[2-¹⁴C,(4R)-4-³H₁], was: ergosterol, 5:3; episterol, 5:4; ergosta-5,7,24(28)-trien-3β-ol, 5:3; 4α-methyl-5α-ergosta-8,24(28)-dien-3β-ol, 5:4; 24-methylene-24,25-dihydrolanosterol, 6:5; lanosterol, 6:5. The significance of these results in terms of ergosterol biosynthesis is discussed.     

The ultrastructure of topical cutaneous calcinosis

Summary Mineralized plaques, which develop at the site of repeated subcutaneous injections of 100 g KMnO₄/0.2 H₂O in rats, were investigated by electron microscopy. The newly formed, delineated, white plaque tissue at the injection site consisted of numerous, mostly unaltered fibroblasts and collagen fibers, without participation of inflammatory cells. Some signs of cell injury were found in the center of the lesions. Numerous, irregularly distributed, small, mineralized foci were seen near the fibroblasts. These were formed by aggregation of small needle-like units (50 Å in diameter and 0.05–2.0 m long). These needle-shaped units were found either in vesicular, cell derived structures, considered to be shed cell processes or cell fragments, or on collagen fibers. Intramitochondrial deposits of such needle-like units were seen frequently. Fusion of smaller mineralized foci to larger plaques occured and then needle-shaped units were seen at the periphery of the electron-dense lesions. Hypotheses concerning the mechanism of experimental cutaneous calcinosis (soft tissue mineralization) are discussed and related to the findings of this study. Probable intracellular crystal deposition and mineralization in cell-derived structures were shown for the first time in topical cutaneous calcinosis.     

AvrRps4 effector family processing and recognition in lettuce

During pathogenesis, effector proteins are secreted from the pathogen to the host plant to provide virulence activity for invasion of the host. However, once the host plant recognizes one of the delivered effectors, effector‐triggered immunity activates a robust immune and hypersensitive response (HR). In planta, the effector AvrRps4 is processed into the N‐terminus (AvrRps4^N) and the C‐terminus (AvrRps4^C). AvrRps4^C is sufficient to trigger HR in turnip and activate AtRRS1/AtRPS4‐mediated immunity in Arabidopsis; on the other hand, AvrRps4^N induces HR in lettuce. Furthermore, AvrRps4^N‐mediated HR requires a conserved arginine at position 112 (R112), which is also important for full‐length AvrRps4 (AvrRps4^F) processing. Here, we show that effector processing and effector recognition in lettuce are uncoupled for the AvrRps4 family. In addition, we compared effector recognition by lettuce of AvrRps4 and its homologues, HopK1 and XopO. Interestingly, unlike for AvrRps4 and HopK1, mutation of the conserved R111 in XopO by itself was insufficient to abolish recognition. The combination of amino acid substitutions arginine 111 to leucine with glutamate 114 to lysine abolished the XopO‐mediated HR, suggesting that AvrRps4 family members have distinct structural requirements for perception by lettuce. Together, our results provide an insight into the processing and recognition of AvrRps4 and its homologues.