Isolation of the outer membrane and characterization of the major outer membrane protein from Spirochaeta aurantia.

The outer membrane of Spirochaeta aurantia was isolated after cells were extracted with sodium lauryl sarcosinate and was subsequently purified by differential centrifugation and KBr isopycnic gradient centrifugation. The purified outer membrane was obtained in the form of carotenoid-containing vesicles. Four protein species with apparent molecular weights of 26,000 (26K), 36.5K, 41K, and 48.5K were readily observed as components of the vesicles. The 36.5K protein was the major polypeptide and constituted approximately 90% of the outer membrane protein observed on sodium dodecyl sulfate-polyacrylamide gels. Under mild denaturing conditions the 36.5K major protein exhibited an apparent molecular weight of approximately 90,000. This, together with the results of protein cross-linking studies, indicates that the 36.5K polypeptide has an oligomeric conformation in the native state. Reconstitution of solubilized S. aurantia outer membrane into lipid bilayer membranes revealed the presence of a porin, presumably the 36.5K protein, with an estimated channel diameter of 2.3 nm based on the measured single channel conductance of 7.7 nS in 1 M KCl.     

Protein synthesis during imaginal disc pattern regulation

We have examined the pattern of protein synthesis during wing disc pattern regulation. Although in vivo culture dramatically alters the pattern of abundant protein synthesis in wing discs, only one protein--RG38--changes specifically in response to pattern regulation. This polypeptide, previously identified as being nonuniformly distributed in wing and haltere discs, is synthesized in a graded distribution across the wing disc. During wing disc pattern regulation, it acts as a molecular marker for regeneration of particular wing disc regions. Thus, the rate of RG38 synthesis increases during regeneration (by fragments with initial low levels) with kinetics that parallel those for regeneration as scored by the presence of adult cuticular structures.     

DNA studies in a family with Duchenne muscular dystrophy and a deletion at Xp21.

We have performed Southern blot analysis on a large, four-generation kindred with Duchenne muscular dystrophy (DMD). Probes 754 (DXS 84), pERT87-1, pERT87-8, pERT87-15 (DXS164), and pXJ-1.1 did not hybridize to digested genomic DNA of affected males. Obligate-carrier mothers and unaffected brothers showed signals of a single X-chromosome copy intensity, and suspected noncarrier sisters demonstrated either a single band of two-copy intensity or informative polymorphisms. Uniform hybridization was seen with probes C7 (DXS28) and D2 (DXS43), which map distal to the DMD locus, and with OTC, which maps proximally. This deletion was present in six affected individuals and has been transmitted through 3 generations to date. On high-resolution chromosome analysis, a deletion within band Xp21 was consistently observed in one affected male studied and in one of the two X chromosomes in obligate carriers. This large molecular and cytogenetically visible deletion in affected DMD individuals without glycerol kinase deficiency, chronic granulomatous disease, retinitis pigmentosa (RP), or ornithine transcarbamylase deficiency is a very rare finding and should prove useful in specifically cloning additional probes within and flanking the DMD locus.     

Glutathione S-transferases in human prostate

A number of human prostatic tissue biopsies have been analyzed for glutathione S-transferase activity, using 1-chloro-2,4-dinitrobenzene (CDNB) as a substrate. Samples from nine patients (age range 61-90) with benign prostatic hypertrophy who had received no prior chemotherapy had a mean glutathione S-transferase activity of 137 +/- 44 nmol/min per mg with a range of 97-237. A qualitative comparison of the glutathione S-transferase of normal prostate and benign prostatic hypertrophy samples was carried out. Approximately 260-fold purification was achieved using glutathione-Sepharose affinity chromatography, with glutathione S-transferase accounting for approximately 0.19-0.33% of the total protein. Substrate specificity determinations suggested similar, but not identical, glutathione S-transferase subunits in normal prostate and benign prostatic hypertrophy. One- and two-dimensional electrophoresis (isoelectric focusing and 12.5% SDS-polyacrylamide gel electrophoresis) identified at least seven stained polypeptides in the purified glutathione S-transferase preparations. These ranged in Mr from approximately 24,000 to 28,500 and in pI from near neutral to basic. Western blot analysis using polyclonal antibodies raised against rat liver glutathione S-transferase suggested crossreactivity with five of the human isoenzymes in both normal prostate and benign prostatic hypertrophy. One of the glutathione S-transferases, present in both normal prostate and benign prostatic hypertrophy, had an Mr of approx. 24,000 and a near-neutral pI and crossreacted immunologically with a polyclonal antibody raised against human placental glutathione S-transferase (Yf, subunit 7 or pi). These data suggest that four glutathione S-transferases are expressed in human prostate, with subunits from each of the major classes alpha, mu and pi. These are characterized as Ya, Yb, Yb' and Yf (analogous alternative nomenclature subunits 1, 3, 4 and 7).     

Factor XIII binds to the A alpha- and B beta- chains in the D-domain of fibrinogen: an immunoblotting study

The binding sites in fibrinogen for Factor XIII were localized using an immunoblotting technique. Platelet Factor XIII bound to fibrinogen and to plasmin degradation products of fibrin(ogen) including Fragments: X, D1-D3, and D-dimer, but did not bind to Fragment E. Binding of Platelet Factor XIII was independent of calcium ions but could be inhibited by the presence of 0.5 M NaCl. Binding could also be inhibited by preincubating Factor XIII with a 100-fold molar excess of fibrinogen but not by 100-fold molar excess of Fragment E. Binding of Factor XIII to fibrinogen was specific, since several other proteins tested (ovalbumin, bovine serum albumin, alpha 2-macroglobulin, beta-galactosidase, fructose kinase, lactic dehydrogenase, triose phosphate isomerase, fumarase and pyruvate kinase) did not bind Factor XIII. Furthermore, binding was not observed either when Factor XIII was left out or when antiFactor XIII antiserum was substituted with nonimmune serum. When fibrinogen was reduced prior to electrophoresis, Factor XIII bound to the A alpha and B beta chains of fibrinogen and des A,B fibrinogen, the B beta-chain of Fragment X, but not the gamma-chains. Localization of the Factor XIII binding sites to the carboxy terminal segments of the A alpha and B beta chains in the Fragment D-domain of fibrinogen could have important physiological consequences.     

Consequences of terbium (111) binding on the conformation and enzymatic activity of Guinea pig liver transglutaminase

Calcium ions are crucial for expression of transglutaminase activity. Although lanthanides have been reported to substitute for calcium in a variety of protein functions, they did not replace the calcium requirement during transglutaminase activity measurements. Furthermore, lanthanides strongly inhibited purified liver transglutaminase activity using either casein or fibrinogen as substrates. Terbium (III) inhibition of transglutaminase-catalyzed putrescine incorporation into casein was not reversed by the presence of 10–200 fold molar excess of calcium ions (Ki for Tb(III)=60 µM). Conformational changes in purified liver transglutaminase upon Tb(III) binding were evident from a biphasic effect of Tb(III) on transglutaminase binding to fibrin. Low concentrations of Tb(III) (1 µM to 10 µM inhibited the binding of transglutaminase to fibrin, whereas higher concentrations (20 µM to 100 µM promoted binding. Conformational changes in purified liver transglutaminase consequent to Tb(III) binding were also demonstrated by fluorescence spectroscopy due to Forster energy transfer. Fluorescence emission was stable to the presence of 200 mM NaCl and 100 mM CaCl₂ only partially quenched emission. Purified liver transglutaminase strongly bound to Tb(III)-Chelating Sepharose beads and binding could not be disrupted by 100 mM CaCl₂ solution. Our data suggest that Tb(III)-induced conformational changes in transglutaminase are responsible for the observed effects on enzyme structure and function. The potential applications of Tb(III)-transglutaminase interactions in elucidating the structure-function relationships of liver transglutaminase are discussed.