Gastric acidity in patients with follicular gastritis is significantly reduced, but can be normalized after eradication for Helicobacter pylori

BACKGROUND: Follicular gastritis is thought to be caused by Helicobacter pylori infection. However, the pathophysiology of it remains unclear. MATERIALS AND METHODS: We assessed gastric acidity in 15 patients with follicular gastritis, aged 20-37 years, using a 24-hour intragastric pH-metry, as well as by histologic and serologic evaluations; and compared it with that in other age-matched groups: 18 cases of H. pylori-positive antrum-predominant gastritis, 12 of pangastritis, and 24 H. pylori-negative normals. In eight cases with follicular gastritis, it was re-assessed 6 months after the eradication therapy for H. pylori. RESULTS: During nighttime, the percentage of time with intragastric pH above 3.0 in follicular gastritis was significantly higher than that in normals (p<.0001), and in antrum-predominant gastritis (p<.001), but was comparable with that in pangastritis. In the daytime period, this parameter in follicular gastritis was significantly higher than that in normal (p<.001), in antrum-predominant gastritis (p<.001), and in pangastritis (p<.05). Marked mononuclear cell and neutrophil infiltration but no apparent glandular atrophy were observed in both the antrum and corpus. Serum pepsinogen I/II ratio was significantly lower in follicular gastritis than that in normals (p<.0001) and in antrum-predominant gastritis (p<.001), whereas serum gastrin was significantly higher than that in normals (p<.0001), in antrum-predominant gastritis (p<.01) and in pangastritis (p<.05). After eradication for H. pylori, all of the parameters in follicular gastritis were altered to the same ranges as those in normals. CONCLUSIONS: In follicular gastritis, gastric acidity is significantly reduced, but can be normalized by eradication of H. pylori. It can thus be speculated that inflammatory cytokines or H. pylori-infection-induced prostaglandins might strongly inhibit gastric acid secretion in follicular gastritis.     

Crystal structure and structural stability of acylphosphatase from hyperthermophilic archaeon Pyrococcus horikoshii OT3

To elucidate the structural basis for the high stability of acylphosphatase (AcP) from Pyrococcus horikoshii OT3, we determined its crystal structure at 1.72 A resolution. P. horikoshii AcP possesses high stability despite its approximately 30% sequence identity with eukaryotic enzymes that have moderate thermostability. The overall fold of P. horikoshii AcP was very similar to the structures of eukaryotic counterparts. The crystal structure of P. horikoshii AcP shows the same fold betaalphabetabetaalphabeta topology and the conserved putative catalytic residues as observed in eukaryotic enzymes. Comparison with the crystal structure of bovine common-type AcP and that of D. melanogaster AcP (AcPDro2) as representative of eukaryotic AcP revealed some significant characteristics in P. horikoshii AcP that likely play important roles in structural stability: (1) shortening of the flexible N-terminal region and long loop; (2) an increased number of ion pairs on the protein surface; (3) stabilization of the loop structure by hydrogen bonds. In P. horikoshii AcP, two ion pair networks were observed one located in the loop structure positioned near the C-terminus, and other on the beta-sheet. The importance of ion pairs for structural stability was confirmed by site-directed mutation and denaturation induced by guanidium chloride.     

Medical sequencing of candidate genes for nonsyndromic cleft lip and palate

Nonsyndromic or isolated cleft lip with or without cleft palate (CL/P) occurs in wide geographic distribution with an average birth prevalence of 1/700. We used direct sequencing as an approach to study candidate genes for CL/P. We report here the results of sequencing on 20 candidate genes for clefts in 184 cases with CL/P selected with an emphasis on severity and positive family history. Genes were selected based on expression patterns, animal models, and/or role in known human clefting syndromes. For seven genes with identified coding mutations that are potentially etiologic, we performed linkage disequilibrium studies as well in 501 family triads (affected child/mother/father). The recently reported MSX1 P147Q mutation was also studied in an additional 1,098 cleft cases. Selected missense mutations were screened in 1,064 controls from unrelated individuals on the Centre d'Étude du Polymorphisme Humain (CEPH) diversity cell line panel. Our aggregate data suggest that point mutations in these candidate genes are likely to contribute to 6% of isolated clefts, particularly those with more severe phenotypes (bilateral cleft of the lip with cleft palate). Additional cases, possibly due to microdeletions or isodisomy, were also detected and may contribute to clefts as well. Sequence analysis alone suggests that point mutations in FOXE1, GLI2, JAG2, LHX8, MSX1, MSX2, SATB2, SKI, SPRY2, and TBX10 may be rare causes of isolated cleft lip with or without cleft palate, and the linkage disequilibrium data support a larger, as yet unspecified, role for variants in or near MSX2, JAG2, and SKI. This study also illustrates the need to test large numbers of controls to distinguish rare polymorphic variants and prioritize functional studies for rare point mutations.     

Link between the ubiquitin conjugation system and the ISG15 conjugation system: ISG15 conjugation to the UbcH6 ubiquitin E2 enzyme

ISG15 is a ubiquitin-like protein that is upregulated on treatment with interferon. ISG15 is considered to be covalently conjugated to cellular proteins through a sequential reaction similar to that of the ubiquitin conjugation system consisting of E1/E2/E3 enzymes: UBE1L and UbcH8 have been reported to function as E1 and E2 enzymes, respectively, for ISG15 conjugation. Several cellular proteins have been identified as targets for ISG15 conjugation, but the roles of ISG15 conjugation remain unclear. In this study, we found that UbcH6 and UbcH8, E2 enzymes for ubiquitin conjugation, are covalently modified by ISG15. We also found that UbcH6 is capable of forming a thioester intermediate with ISG15 through Cys131. We determined that the Lys136 residue near the catalytic site Cys131 is the ISG15 conjugation site in UbcH6. We isolated ISG15-modified and unmodified UbcH6 proteins, and analyzed their abilities to form thioester intermediates with ubiquitin. A ubiquitin thioester intermediate was detected in the case of unmodified UbcH6, but not in that of ISG15-modified UbcH6, strongly suggesting that ISG15 conjugation to UbcH6 suppresses its ubiquitin E2 enzyme activity. Thus, we provide evidence for a link between the ubiquitin conjugation system and the ISG15 conjugation system.     

BIG1 is a binding partner of myosin IXb and regulates its Rho-GTPase activating protein activity

Myosin IXb, a member of the myosin superfamily, is a molecular motor that possesses a GTPase activating protein (GAP) for Rho. Through the yeast two-hybrid screening using the tail domain of myosin IXb as bait we found BIG1, a guanine nucleotide exchange factor for ADP-ribosylation factor (Arf1), as a potential binding partner for myosin IXb. The interaction between myosin IXb and BIG1 was demonstrated by co-immunoprecipitation of endogenous myosin IXb and BIG1 with anti-BIG1 antibodies in normal rat kidney cells. Using the isolated proteins, it was demonstrated that myosin IXb and BIG1 directly bind to each other. Various truncation mutants of the myosin IXb tail domain were produced, and it was revealed that the binding region of myosin IXb to BIG1 is the zinc finger/GAP domain. Interestingly, the GAP activity of myosin IXb was significantly inhibited by the addition of BIG1 with IC(50) of 0.06 microm. The RhoA binding to myosin IXb was inhibited by the addition of BIG1 with the concentration similar to the inhibition of the GAP activity. Likewise, RhoA inhibited the BIG1 binding of myosin IXb. These results suggest that BIG1 and RhoA compete with each other for the binding to myosin IXb, thus resulting in the inhibition of the GAP activity by BIG1. The present study identified BIG1, the Arf guanine nucleotide exchange factor, as a new binding partner for myosin IXb, which inhibited the GAP activity of myosin IXb. The findings raise a concept that the myosin transports the signaling molecule as a cargo that functions as a regulator for the myosin molecule.     

Effect of deuterium oxide on contraction characteristics and ATPase activity in glycerinated single rabbit skeletal muscle fibers

We studied the effect of deuterium oxide (D(2)O) on contraction characteristics and ATPase activity of single glycerinated muscle fibers of rabbit psoas. D(2)O increased the maximum isometric force P(0) by about 20%, while the force versus stiffness relation did not change appreciably. The maximum shortening velocity under zero load V(max) did not change appreciably in D(2)O, so that the force-velocity (P-V) curve was scaled depending on the value of P(0). The Mg-ATPase activity of the fibers during generation of steady isometric force P(0) was reduced by about 50% in D(2)O. Based on the Huxley contraction model, these results can be accounted for in terms of D(2)O-induced changes in the rate constants f(1) and g(1) for making and breaking actin-myosin linkages in the isometric condition, in such a way that f(1)/(f(1)+g(1)) increases by about 20%, while (f(1)+g(1)) remains unchanged. The D(2)O effect at the molecular level is discussed in connection with biochemical studies on actomyosin ATPase.     

Acid denaturation and refolding of green fluorescent protein

Green fluorescent protein from the jellyfish Aequorea victoria can serve as a good model protein to understand protein folding in a complex environment with molecular chaperones and other macromolecules such as those in biological cells, but little is known about the detailed mechanisms of the in vitro folding of green fluorescent protein itself. We therefore investigated the kinetic refolding of a mutant (F99S/M153T/V163A) of green fluorescent protein, which is known to mature more efficiently than the wild-type protein, from the acid-denatured state; refolding was observed by chromophore fluorescence, tryptophan fluorescence, and far-UV CD, using a stopped-flow technique. In this study, we demonstrated that the kinetics of the refolding of the mutant have at least five kinetic phases and involve nonspecific collapse within the dead time of a stopped-flow apparatus and the subsequent formation of an on-pathway intermediate with the characteristics of the molten globule state. We also demonstrated that the slowest phase and a major portion of the second slowest phase were rate-limited by slow prolyl isomerization in the intermediate state, and this rate limitation accounts for a major portion of the observed kinetics in the folding of green fluorescent protein.