The carboxyl-terminal domain of colicin E5 was shown to inhibit protein synthesis of Escherichia coli. Its target, as revealed through in vivo and in vitro experiments, was not ribosomes as in the case of E3, but the transfer RNAs (tRNAs) for Tyr, His, Asn, and Asp, which contain a modified base, queuine, at the wobble position of each anticodon. The E5 carboxyl-terminal domain hydrolyzed these tRNAs just on the 3' side of this nucleotide. Tight correlation was observed between the toxicity of E5 and the cleavage of intracellular tRNAs of this group, implying that these tRNAs are the primary targets of colicin E5.

Colicin D has long been thought to stop protein synthesis in infected Escherichia coli cells by inactivating ribosomes, just like colicin E3. Here, we show that colicin D specifically cleaves tRNAs Arg including four isoaccepting molecules both in vivo and in vitro. The cleavage occurs in vitro between positions 38 and 39 in an anticodon loop with a 2 ,3 -cyclic phosphate end, and is inhibited by a specific immunity protein. Consistent with the cleavage of tRNAs Arg , the RNA fraction of colicin-treated cells significantly reduced the amino acid-accepting activity only for arginine. Furthermore, we generated a single mutation of histidine in the C-terminal possible catalytic domain, which caused the loss of the killing activity in vivo together with the tRNA Arg -cleaving activity both in vivo and in vitro. These findings show that colicin D directly cleaves cytoplasmic tRNAs Arg , which leads to impairment of protein synthesis and cell death. Recently, we found that colicin E5 stops protein synthesis by cleaving the anticodons of specific tRNAs for Tyr, His, Asn, and Asp. Despite these apparently similar actions on tRNAs and cells, colicins D and E5 not only exhibit no sequence homology but also have different molecular mechanisms as to both substrate recognition and catalytic reaction.C olicins are plasmid-encoded proteins that are toxic to Escherichia coli cells that do not have the same plasmid or a cognate Col plasmid (1-5). Most colicins are produced in response to SOS-inducing signals and are secreted into the medium. After binding to cell-surface receptors on sensitive cells, they are translocated across the membrane and then exert their final cytotoxic activities, which are attributable to their C-terminal domains. Two major modes of toxicity are well known; colicins A, B, E1, Ia, Ib, K, and N are ion-channel formers attacking the cytoplasmic membrane, and colicins E2 to E9 are nucleases. In the latter group, E2, E7, E8, and E9 are DNases, and E3 is a special kind of RNase that cleaves 16S rRNA within ribosomes.Colicins E4 to E6 quickly stop amino acid incorporation in treated cells (6), suggesting impairment of protein synthesis analogous in the established case of E3, which specifically cleaves 16S-RNA at the 49th bond from the 3Ј end leading to inactivation of ribosomes (7-9). This is also the case with colicin D, which Timmis and Hedges have characterized as to the physiological response of treated cells (10, 11), although the actual molecular basis of the cytotoxic effect of colicin D, as well as those of E4 to E6, remained to be elucidated. Colicins E4 and E6 proved to be E3-homologs and showed comparable activity toward ribosomes (ref. 12; GenBank accession number X63621; Y. Gunji, M. Ohno, T.O., H.M., and T.U., unpublished data), but colicin E5 exhibits no similarity to E3 in the C-terminal active domain. We recently showed that colicin E5 comprises a third category of nuclease-type colicins, which does not attack ribosomes but specific tRNAs (13). E5 is a novel RNase that cleaves the anticodons...

BACKGROUND AND PURPOSE:Quantitative susceptibility mapping allows overcoming several nonlocal restrictions of susceptibilityweighted and phase imaging and enables quantification of magnetic susceptibility. We compared the diagnostic accuracy of quantitative susceptibility mapping and R2* (1/T2*) mapping to discriminate between patients with Parkinson disease and controls.

There is little evidence for multisession repetitive transcranial magnetic stimulation (rTMS) on pain relief in patients with neuropathic pain (NP), although single-session rTMS was suggested to provide transient pain relief in NP patients. We aimed to assess the efficacy and safety of 10 daily rTMS in NP patients. We conducted a randomized, double-blind, sham-controlled, crossover study at 7 centers. Seventy NP patients were randomly assigned to 2 groups. A series of 10 daily 5-Hz rTMS (500 pulses/session) of primary motor cortex (M1) or sham stimulation was applied to each patient with a follow-up of 17days. The primary outcome was short-term pain relief assessed using a visual analogue scale (VAS). The secondary outcomes were short-term change in the short form of the McGill pain questionnaire (SF-MPQ), cumulative changes in the following scores (VAS, SF-MPQ, the Patient Global Impression of Change scale [PGIC], and the Beck Depression Inventory [BDI]), and the incidence of adverse events. Analysis was by intention to treat. This trial is registered with the University hospital Medical Information Network Clinical Trials Registry. Sixty-four NP patients were included in the intention-to-treat analysis. The real rTMS, compared with the sham, showed significant short-term improvements in VAS and SF-MPQ scores without a carry-over effect. PGIC scores were significantly better in real rTMS compared with sham during the period with daily rTMS. There were no significant cumulative improvements in VAS, SF-MPQ, and BDI. No serious adverse events were observed. Our findings demonstrate that daily high-frequency rTMS of M1 is tolerable and transiently provides modest pain relief in NP patients.

Abstract.The pituitary function of patients with Rathke's cleft cyst before and after surgery was investigated to clarify the significance of surgery and operative indications.The authors have treated 19