Structural and functional differentiation of two clinally distributed glucosephosphate isomerase allelic isozymes from the teleost Fundulus heteroclitus

The teleost Fundulus heteroclitus (L.) possesses two loci, Gpi-A and Gpi-B, for the glycolytic enzyme, glucose-phosphate isomerase (GPI; D- glucose-6-phosphate ketol-isomerase; E.C. 5.3.1.9). The Gpi-B locus is polymorphic in Fundulus, with two common alleles, Gpi-Bb and Gpi-Bc, distributed in a clinal manner in populations along the east coast of North America. Since this clinal distribution is strongly correlated with a temperature gradient, we asked whether the GPI-B2 allozymes were functionally adapted to the thermal environment in which a given phenotype predominated. The two major GPI-B2 allozymes were purified to homogeneity and were characterized as to molecular weight, isoelectric pH, thermal denaturation, and kinetic parameters. Both GPI-Bb2 and GPI- Bc2 allozymes have molecular masses of 110 kD, and they have isoelectric pHs of 6.4 and 6.6, respectively. The GPI-Bb2 allozyme was more stable to thermal denaturation than was the GPI-Bc2 enzyme. Kinetic properties of the allelic isozymes were investigated both as a function of pH and as a function of temperature. At 25 degrees C, over the pH range considered, there were no significant differences between allozymes, either in Km for fructose-6-phosphate or in Ki for 6- phosphogluconate, but apparent Vmax values differed between pH 7.5 and pH 8.5. All steady-state kinetic parameters showed strong temperature dependence, but the allozymes differed only in the Ki for 6- phosphogluconate at temperatures greater than 30 degrees C. On the basis of the observed structural and functional differences alluded to above, the hypothesis that the major allelic isozymes of the Gpi-B locus were functionally equivalent was rejected. However, it is not yet known whether these structural and functional differences have any significance at higher levels of biological organization.      

Regulation by a novel protein of the bimodal distribution of lipopolysaccharide in the outer membrane of Escherichia coli.

We report on the cloning and characterization of the rfb gene cluster of the O75 lipopolysaccharide from a urinary tract isolate of Escherichia coli. Deletion cloning defined the minimum region of DNA that expressed the O75 antigen in E. coli host strains to be on a 12.4-kb insert. However, the E. coli strain expressing this region did not produce a polymerized O chain as detected by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and silver staining. A slightly larger DNA clone of 13.4 kb produced a polymerized O chain in E. coli S phi 874 but was found to be abnormal in its distribution over the surface membrane. Normal wild-type E. coli, as with Salmonella spp., has a bimodal distribution of the lipopolysaccharide on the surface which is seen as an abundance of long and short O chains attached to the lipid A-core structure. We found in a region adjacent to the cloned rfb region, and on the opposite side from where the putative polymerase (rfc) is encoded, a novel protein of 35.5 kDa expressed from a 1.75-kb DNA fragment. This protein was shown to complement in trans the E. coli strains carrying plasmids that expressed abnormal, unregulated lipopolysaccharides. The expression of these complemented strains was bimodal in distribution. Mutation of the gene encoding this protein destroyed its ability to regulate O-chain distribution. We propose to call this regulator gene rol, for regulator of O length.     

Identification of kex2-related proteases in chromaffin granules by partial amino acid sequence analysis

We have characterized glycoprotein H (GpH) from bovine adrenal medullary chromaffin granules. Two-dimensional gel electrophoresis was used to purify GpH from an insoluble fraction obtained following extraction of chromaffin granule membranes with lithium diiodosalicylate. The GpH material was recovered from two-dimensional gel spots by concentration and recovery on a one-dimensional gel followed by electro-blotting to a poly(vinylidene difluoride) membrane. This material was subjected to in situ tryptic digestion. The released peptides were purified by microbore high performance liquid chromatography and sequenced. The peptide sequences revealed extensive similarity to the mammalian kex2/subtilisin-related proteases (PC2 and PC3) which have been characterized recently by molecular cloning and sequence analysis (Smeekens, S. P., and Steiner, D. F. (1990) J. Biol. Chem. 265, 2997-3000; Smeekens, S. P., Avruch, A. S., LaMendola, J., Chan, S. J., and Steiner, D. F. (1991) Proc. Natl. Acad. Sci. U.S.A. 88, 340-344). The sequence similarity included regions that contain residues equivalent to the aspartic acid and histidine residues which are involved in the active site of the subtilisin family of serine proteases. The sequence data revealed the presence of tryptic peptides derived from both PC2 and PC3. NH2-terminal sequence analysis of GpH gave two sequences which were aligned with residues 110-121 of PC2 and PC3. It is likely that these sequences represent the mature form of PC2 and PC3 in chromaffin granules. These forms would be generated by cleavage at a site which is conserved in mammalian kex2-related enzymes and which would result in the release of approximately 80-residue propeptides. It was concluded that the spot identified as GpH by two-dimensional gel electrophoresis contains the bovine counterparts of both PC2 and PC3. The direct identification of these components in chromaffin granules supports their role in the processing of protein precursors.     

Echocardiographic assessment and percutaneous closure of multiple atrial septal defects

Percutaneous coronary intervention can be associated with distal embolization of thrombotic material causing myocardial necrosis and infarction. We discuss the role of intravascular imaging to guide the use of a distal protection device by describing the outcome of a young woman presenting with non-ST elevation myocardial infarction. Coronary angiography demonstrated an isolated minor stenosis in the proximal left anterior descending coronary artery with slight haziness beyond the lesion. Intravascular ultrasound confirmed an extensive thrombus overlying a bulky atherosclerotic plaque. A distal filter wire was therefore successfully used to reduce the risk of distal embolization. The use of intravascular ultrasound in patients presenting with acute coronary syndrome may reveal large thrombi that are difficult to image using conventional angiographic techniques. Intravascular ultrasound can therefore be used as a tool to select lesions requiring distal protection.     

VEGF-targeted cancer therapy strategies: current progress, hurdles and future prospects

Despite setbacks, the clinical development of antiangiogenic agents has accelerated remarkably over the past 3-4 years. Consequently, there are currently three direct inhibitors of the VEGF pathway approved for use in cancer therapy. Other agents that block the VEGF pathway are in advanced stages of clinical development and have shown promising results. With these exciting developments come crucial questions regarding the use of these new molecular-targeted agents, alone or in combination with standard cytotoxic or targeted agents. Importantly, the mechanisms of action of anti-VEGF therapy remain unknown. Here, we discuss several potential mechanisms of action such as tumor vascular normalization, bone marrow-derived cell recruitment blockade and cytostatic effects of anti-VEGF therapy. We review the current progress, the major stumbling blocks and the future directions for anti-cancer therapy using anti-VEGF agents, emphasizing clarification of the underlying molecular mechanisms of action and biomarker identification and validation.     

Volatile emission by contest losers revealed by real-time chemical analysis

Animal interactions often involve chemical exchange but simultaneous evaluation of chemistry and behaviour has been problematical. Here we report findings from a novel method, atmospheric pressure chemical ionization-mass spectrometry (APCI-MS) coupled with manipulation of molecular-mass achieved by rearing organisms on deuterium-enhanced nutrients. This allows real-time monitoring of the occurrence and quantity of volatile chemicals released by each of two interacting individuals, in tandem with behavioural observations. We apply these methods to female-female contests in the parasitoid wasp Goniozus legneri. We show that this species emits the spiroacetal 2-methyl-1,7-dioxaspiro[5.5]undecane. Chemical release is most common in more behaviourally aggressive contests, which occur when prior resource owners successfully resist take-over by similar-sized intruder females. Volatiles released during contests are always emitted by the loser. Aggression in contests is reduced after spiroacetal release. We suggest that the spiroacetal functions as a weapon of rearguard action. We anticipate that APCI-MS, which is rapid, non-intrusive and relatively inexpensive to operate, will be widely applied in studies linking chemistry and behaviour.