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Abstract: RsmE is the founding member of a new RNA methyltransferase (MTase) family responsible for methylation of U1498 in 16S ribosomal RNA in Escherichia coli. It is well conserved across bacteria and plants and may play an important role in ribosomal intersubunit communication. The crystal structure in monomer showed that it consists of two distinct but structurally related domains: the PUA (pseudouridine synthases and archaeosine‐specific transglycosylases)-like RNA recognition and binding domain and the conserved MTase domain with a deep trefoil knot. Analysis of small-angle X-ray scattering data revealed that RsmE forms a flexible dimeric conformation that may be essential for substrate binding. The S‐adenosyl‐l‐methionine (AdoMet)-binding characteristic determined by isothermal titration calorimetry suggested that there is only one AdoMet molecule bound in the subunit of the homodimer. In vitro methylation assay of the mutants based on the RsmE–AdoMet–uridylic acid complex model showed key residues involved in substrate binding and catalysis. Comprehensive comparisons of RsmE with closely related MTases, combined with the biochemical experiments, indicated that the MTase domain of one subunit in dimeric RsmE is responsible for binding of one AdoMet molecule and catalytic process while the PUA-like domain in the other subunit is mainly responsible for recognition of one substrate molecule (the ribosomal RNA fragment and ribosomal protein complex). The methylation process is required by collaboration of both subunits, and dimerization is functionally critical for catalysis. In general, our study provides new information on the structure–function relationship of RsmE and thereby suggests a novel catalytic mechanism. [Copyright &y& Elsevier]

Objective: To investigate the surgical procedure, clinical efficacy, complications, density of endothelial cells and histological changes after Descemet's stripping endothelial keratoplasty (DSEK) surgery., Methods: It was a experimental study. Twenty four New Zealand rabbits were divided into 3 groups, 8 rabbits per group. Donor grafts were dissected from 16 New Zealand rabbit eyes. Group A was experimental group, a 5 mm limbal tunnel incision was made. Descemet's membrane was striped off at 10 mm diameter, then the same diameter donor cornea (including Descemet's membrane and endothelium with a little of posterior stroma) was inserted into the recipient's anterior chamber. Air was injected into the anterior chamber to press the graft up against the recipient cornea. Group B was the control group, only striped the Descemet's membrane at the recipient cornea. Group C was the experiment control group, the procedure was similar to the group A, but the donor graft was without endothelial cells., Results: All corneas of group A were transparent, and the mean density of the endothelial cells was (2195 +/- 77)/mm2 (t = 12.455, P < 0.001). Endothelial grafts attached to the recipients well and no scar formation between them under histological observation. The corneas were severe edema in groups B and C one month after surgery., Conclusions: DSEK is a safe surgery, can be recovered rapidly with little damages, and without interface scar formation after surgery. DSEK may be the first choice for the treatment of bullous keratopathy.

Rachycentron canadum is a thriving mariculture species for offshore cage in southern Mainland and Taiwan of China, due to its rapid growth rate and high quality flesh. In this paper, the gill Na(+)-K+ ATPase (NKA) activity and iono- and osmoregulation of juvenile R. canadum were investigated in a 12 h stress of ambient salinities (0-45), and the results showed that after an abrupt transfer to the salinities of 0, 5, 15, 25, 37 (control) and 45, the death of juvenile R. canadum only occurred in salinity 0, with a mortality of 100% by the end of the experiment. In all treatments, the gill NKA activity and serum osmolality fluctuated in first 3 h, and then changed smoothly. The NKA activity varied with salinity grade in U shape, being significantly (P < 0.05) higher in salinity 5 and the lowest in salinity 15 in 12 h, while the serum osmolality (ranged 293-399 mOsmol x kg(-1)) presented a positive correlation with salinity. Serum [Na+] and [Cl-] concentration slightly increased with salinity within the period of 3-12 h, while serum [K+] displayed a reverse pattern. The isosmotic point was estimated as 328.2 mOsm x kg(-1) and corresponded to salinity 11.48. The isoionic points for serum [Na+], [K+] and [Cl-] were estimated as 155.2, 6.16, and 137.1 mmol x L(-1), which corresponded to the salinities of 10.68, 20.44 and 8.41, respectively. It was concluded that R. canadum could be characterized physiologically as a "higher-NKA-in-hyposmotic media" marine euryhaline teleost with the capability of rapid and effective hyper/hypo iono- and osmoregulation.