Two frameshift mutations in the cystic fibrosis gene

Cystic fibrosis (CF) is a recessive disease caused by mutations in the CF transmembrane conductance regulator (CFTR) gene. We have identified in exon 7 two frameshift mutations, one caused by a two-nucleotide insertion and the other caused by a one-nucleotide deletion; these mutations--CF1154insTC and CF1213delT, respectively, are predicted to shift the reading frame of the protein and to introduce UAA(ochre) termination codons at residues 369 and 368.     

Carboxyphosphonoenolpyruvate phosphonomutase, a novel enzyme catalyzing C-P bond formation.

An enzyme catalyzing the formation of an unusual C-P bond that is involved in the biosynthesis of the antibiotic bialaphos (BA) was isolated from the cell extract of a mutant (NP71) of Streptomyces hygroscopicus SF1293. This enzyme, carboxyphosphonoenolpyruvate (CPEP) phosphonomutase, was first identified as a protein lacking in a mutant (NP213) defective in one of the steps in the pathway to BA. The first 30 residues of the amino terminus of this protein were identical to those predicted by the nucleotide sequence of the gene that restored BA production to NP213. The substrate of the enzyme, a P-carboxylated derivative of phosphoenolpyruvate named CPEP, was also isolated from the broth filtrate of NP213 as a new biosynthetic intermediate of BA. CPEP phosphonomutase catalyzes the rearrangement of the carboxyphosphono group of CPEP to form the C-P bond of phosphinopyruvate.     

Immunoaffinity purification of type I protein kinase C

We designed a simple procedure for the purification of type I protein kinase C, using immunoaffinity chromatography with a monoclonal antibody, MC-1b, obtained by rescreening hybridoma cells available for an affinity ligand. Western blotting demonstrated that MC-1b specifically reacted with type I protein kinase C, and the enzyme molecule dissociated from MC-1b-coupled Sepharose 4B with mild eluants such as thiocyanate retained the kinase activity. A 1148-fold purification was achieved and 210 micrograms of type I protein kinase C was obtained from three rabbit brains, by means of a two-step procedure, using DEAE-cellulose and immunoaffinity chromatography. The resultant preparation was homogeneous, as indicated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis hydroxylapatite chromatography, and immunological analysis using MC-1a, MC-2a, and MC-3a.     

Ca2+ regulated modulator protein interacting agents: inhibition of Ca2+-Mg2+-ATPase of human erythrocyte ghost.

Agents such as N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide (W-7), and its derivatives, chlorpromazine and amitriptyline that interact with calcium-regulated modulator protein were found to inhibit not only Ca²⁺ dependent cyclic nucleotide phosphodiesterase but also Ca²⁺-Mg²⁺-ATPase of human erythrocyte ghosts. I₅₀ values of modulator interacting agents for testis modulator-activated, brain modulator-activated and erythrocyte modulator-activated-ATPase are indistinguishable. However, I₅₀ of W-7 for troponin C-activated-ATPase is lower than that for modulator-activated ATPase. The specificity of these agents toward modulator-related enzyme reaction is also shown by the negative effect on modulator-unrelated enzyme system such as erythrocyte ghost protein kinase and Mg²⁺-ATPase. These agents provide a useful tool for elucidating the physiological role of modulator.     

CYCLIC NUCLEOTIDE PHOSPHODIESTERASE OF HUMAN CEREBROSPINAL FLUID

Abstract— Cyclic 3',5'-AMP (cAMP) and cyclic 3',5'–GMP (cGMP) phosphodiesterase activities were found in human cerebrospinal fluid (CSF) using low substrate concentration (0.4μM). More rapid hydrolysis of cGMP than that of cAMP was observed in human CSF. However, cGMP hydrolytic activity of CSF was very much lower (0.3 pmol/min/ml CSF) than that of human cerebral cortex (33.7 nmol/min/g wet cortex). The pH optimum was found to be 8.0 (cGMP phosphodiesterase) and 7.5 (cAMP phosphodiesterase). The maximum stimulation of both cAMP and cGMP phosphodiesterase was achieved at 4 mM-MgCl₂. Cyclic AMP had relatively little effect on the hydrolysis of cGMP in CSF and the cortex, while cGMP inhibited hydrolysis of cAMP in both tissues. Snake venom was found to stimulate cAMP and cGMP phosphodiesterase activity of CSF, by 60% and 110% respectively. This stimulation by snake venom was also observed in the cortex phosphodiesterase, but was not observed in human plasma or thyroid phosphodiesterase. When CSF was applied to Sepharose 6B column, cGMP phosphodiesterase was separated into three different molecular forms. A plot of activity against substrate concentration using peak I (largest molecular size) revealed a high affinity ( K _m= 2.6μM) and a low affinity ( K _m= 100μM) for cAMP suggesting the existence of at least two molecular forms of the enzyme. On the other hand, using a cGMP as substrate the only one K _m value (1.90 μm) was obtained. These K _m values of CSF enzymes described above were close to those obtained from human cerebral cortex preparations. The enzyme under peak I corresponded to the cortex enzyme when judged from its molecular size and stimulation by snake venom. It seems likely from our results that at least a part of CSF phosphodiesterase originates from the central nervous system.     

Functional Analysis of Deep Intronic SNP rs13438494 in Intron 24 of PCLO Gene

The single nucleotide polymorphism (SNP) rs13438494 in intron 24 of PCLO was significantly associated with bipolar disorder in a meta-analysis of genome-wide association studies. In this study, we performed functional minigene analysis and bioinformatics prediction of splicing regulatory sequences to characterize the deep intronic SNP rs13438494. We constructed minigenes with A and C alleles containing exon 24, intron 24, and exon 25 of PCLO to assess the genetic effect of rs13438494 on splicing. We found that the C allele of rs13438494 reduces the splicing efficiency of the PCLO minigene. In addition, prediction analysis of enhancer/silencer motifs using the Human Splice Finder web tool indicated that rs13438494 induces the abrogation or creation of such binding sites. Our results indicate that rs13438494 alters splicing efficiency by creating or disrupting a splicing motif, which functions by binding of splicing regulatory proteins, and may ultimately result in bipolar disorder in affected people.