Biochemical analyses reveal new insights into RCAN1/Rcn1 inhibition of calcineurin.

Calcineurin is a serine/threonine protein phosphatase that is highly conserved from yeast to human and plays a critical role in many physiological processes. Regulators of calcineurin (RCANs) are a family of endogenous calcineurin regulators, which are capable of inhibiting the catalytic activity of calcineurin in vivo and in vitro. In this study, we first characterized the biochemical properties of yeast calcineurin and its endogenous regulator Rcn1, a yeast homolog of RCAN1. Our data show that Rcn1 inhibits yeast calcineurin toward pNPP substrate with a noncompetitive mode; and Rcn1 binds cooperatively to yeast calcineurin through multiple low-affinity interactions at several docking regions. Next, we reinvestigated the mechanism underlying the inhibition of mammalian calcineurin by RCAN1 using a combination of biochemical, biophysical, and computational methods. In contrast to previous observations, RCAN1 noncompetitively inhibits calcineurin phosphatase activity toward both pNPP and phospho-RII peptide substrates by targeting the enzyme active site in part. Re-analysis of previously reported kinetic data reveals that the RCAN1 concentrations used were too low to distinguish between the inhibition mechanisms [Chan B et al. (2005) Proc Natl Acad Sci USA 102, 13075]. The results presented in this study provide new insights into the interaction between calcineurin and RCAN1/Rcn1.

[Intravenous contrast imaging in diagnosis of acute renal allograft rejection: a comparative study with color flow Doppler imaging].

OBJECTIVE: To assess the value of intermittent contrast second harmonic imaging (SHI) incorporating acoustic densitometry in the diagnosis of acute renal allograft rejection in comparison with color Doppler flow imaging (CDFI) for determining the resistance index (RI). METHODS: Eight canine models of acute renal allograft rejection were established, subjected subsequently to examinations with SHI and acoustic densitometry to determine the acoustic density. Color flow Doppler was also performed to determine RI, and serum creatinine (Cr) levels were measured. RESULTS: The time-intensity curve (TIC) showed that the area under the curve, the peak intensity (PI) and RI all had linear correlation with serum Cr levels, with the correlation coefficient gamma of 0.978, 0.972 and 0.708 respectively (by SPSS10.0). CONCLUSION: Intermittent contrast SHI is effective to evaluate the perfusion of renal allograft, and when combined with acoustic densitometry, the resultant TIC parameters are in closer correlation with acute renal allograft rejection than RI.

Sequence-specific assignments of proton NMR resonance peaks and analysis of secondary structural elements of LC1, a novel antibacterial polypeptide.

LC1 is a type of novel antibacterial polypeptide secreted by a Bacillus subtilis strain. It consists of 47 residues. Using bioengineering, LC1 was expressed in E.coli DH5alpha by using recombinant plasmid PBVAB16. By means of two-dimensional DQF-COSY, TOCSY and NOESY spectroscopies, protons of all 47 residues are identified. The studies show that the secondary structures of LC1 are principally anti-parallel beta sheets and extended conformations. It was speculated that there may be a hydrophobic core around Trp(23) in its three-dimensional structure.