Activation of erythrocyte membrane Ca2+-ATPase by calpain

Ca2+-ATPase of erythrocyte membranes, prepared from erythrocytes substantially removed of contaminating leukocytes, was found to be activated by calpain isolated from the same source. Saponin or glycodeoxycholate treatment of membranes was essential for elicitation of the calpain response. Unlike the membrane bound ATPase, solubilized ATPase was inactivated by calpain. Digestion of membranes with the protease did not affect the Km (ATP) of Ca2+-ATPase though stimulation of the membrane ATPase by calmodulin could be partially substituted by calpain treatment. As compared with control, Ca2+-ATPase of calpain-digested membranes attained maximal activity at a lower free Ca2+ concentration.     

Cloning of the cyo locus encoding the cytochrome o terminal oxidase complex of Escherichia coli.

The structural genes encoding the cytochrome o terminal oxidase complex (cyo) of Escherichia coli have been subcloned into the multicopy plasmid pBR322 after the Mu-mediated transposition of the gene locus from the bacterial chromosome onto the conjugative R plasmid RP4. Introduction of cyo plasmids into strains (cyo cyd) lacking both terminal oxidases restored the ability of the strains to grow aerobically on nonfermentable substrates. Strains carrying the cyo plasmids produced 5 to 10 times more cytochrome o oxidase than did control strains. The gene products encoded by the cyo plasmids could be immunoprecipitated with monospecific antibodies raised against cytochrome o. The cloned genes will be valuable for studying the structure, function, and regulation of the cytochrome o terminal oxidase complex.     

Expression of cDNAs encoding wild-type and mutant neuromodulins in Escherichia coli: comparison with the native protein from bovine brain

Murine cDNA that encodes neuromodulin, a neurospecific calmodulin binding protein, was inserted into the plasmid pKK223-3 for expression in Escherichia coli. After being transformed into E. coli strain SG20252 (lon-), the expression vector directed the synthesis of a protein that was recognized by polyclonal antibodies raised against bovine neuromodulin. The recombinant protein expressed in E. coli was found to be tightly associated with insoluble cell material and was extractable only with guanidine hydrochloride or sodium dodecyl sulfate. Following solubilization with guanidine hydrochloride, the protein was purified to apparent homogeneity by a single CaM-Sepharose affinity column step with a yield of 0.2 mg of protein/L of E. coli culture. The availability of the purified recombinant neuromodulin made it possible to answer several specific questions concerning the structure and function of the protein. Despite the fact that murine neuromodulin is 12 amino acid residues shorter than the bovine protein and the recombinant protein expressed in E. coli may lack any posttranslational modifications, the two proteins displayed similar biochemical properties in almost all respects examined. They both had higher affinity for CaM-Sepharose in the absence of Ca2+ than in its presence; they were both phosphorylated in vitro by protein kinase C in a Ca2+- and phospholipid-dependent manner; neither form of the proteins was autophosphorylated, and the phosphorylated form of the proteins did not bind calmodulin. The recombinant neuromodulin and neuromodulin purified from bovine brain had similar, but not identical, affinities of calmodulin, indicating that the palmitylation of the protein that occurs in animal cells is not crucial for calmodulin interactions.(ABSTRACT TRUNCATED AT 250 WORDS)     

Phylogenetic distribution in the genus Mus of t-complex-specific DNA and protein markers: inferences on the origin of t-haplotypes

We have examined the phylogenetic distribution of two t-specific markers among representatives of various taxa belonging to the genus Mus. The centromeric TCP-1a marker (a testicular protein variant specific for all t-haplotypes so far studied) has also been apparently detected in several non-t representatives of the Mus IVA, Mus IVB, and probably M. cervicolor species. By contrast, a t-specific restriction- fragment-length polymorphism allele (RFLP) of the telomeric alpha- globin pseudogene DNA marker alpha-psi-4 was found only in animals belonging to the M. musculus-complex species either bearing genuine t- haplotypes or, like the M. m. bactrianus specimen studied here, likely to do so. This t-specific alpha-psi-4 RFLP allele was found to be as divergent from the RFLP alleles of the latter, non-t, taxonomical groups as it is from Mus 4A, Mus 4B, or M. spretus ones. These results suggest the presence of t-haplotypes and of t-specific markers in populations other than those belonging to the M. m. domesticus and M. m. musculus subspecies, implying a possible origin for t-haplotypes prior to the radiation of the most recent offshoot of the Mus genus (i.e., the spretus/domesticus divergence), some 1-3 Myr ago.      

Role of quinones in the branch of the Escherichia coli respiratory chain that terminates in cytochrome o.

The role of quinones in the cytochrome o branch of the Escherichia coli respiratory chain was investigated by using mutant strains lacking the cytochrome d terminal oxidase complex. The only cytochromes present were cytochrome b556 and the cytochrome o complex, consisting of cytochrome b555-b562. Mutant strains missing ubiquinone, menaquinone, or both were constructed in the cytochrome d-minus (cyd) background. The steady-state levels of cytochrome b reduction were examined and compared in these strains to assess the effects of the quinone deficiencies. The data clearly show that a ubiquinone deficiency results in a lower level of cytochrome b reduction in the steady state. The data are consistent with a simple model in which ubiquinone is placed on the dehydrogenase side of all the cytochromes in this branch of the respiratory chain. There is no evidence from these experiments for a role of quinones in the respiratory chain at any site besides this one.     

The contractile basis of amoeboid movement: V. The control of gelation, solation, and contraction in extracts from dictyostelium discoideum

Motile extracts have been prepared from Dictyostelium discoideum by homogenization and differential centrifugation at 4 degrees C in a stabilization solution (60). These extracts gelled on warming to 25 degrees Celsius and contracted in response to micromolar Ca++ or a pH in excess of 7.0. Optimal gelation occurred in a solution containing 2.5 mM ethylene glycol-bis (β-aminoethyl ether)N,N,N',N'-tetraacetate (EGTA), 2.5 mM piperazine-N-N'-bis [2-ethane sulfonic acid] (PIPES), 1 mM MgC1(2), 1 mM ATP, and 20 mM KCI at ph 7.0 (relaxation solution), while micromolar levels of Ca++ inhibited gelation. Conditions that solated the gel elicited contraction of extracts containing myosin. This was true regardless of whether chemical (micromolar Ca++, pH >7.0, cytochalasin B, elevated concentrations of KCI, MgC1(2), and sucrose) or physical (pressure, mechanical stress, and cold) means were used to induce solation. Myosin was definitely required for contraction. During Ca++-or pH-elicited contraction: (a) actin, myosin, and a 95,000-dalton polypeptide were concentrated in the contracted extract; (b) the gelation activity was recovered in the material sqeezed out the contracting extract;(c) electron microscopy demonstrated that the number of free, recognizable F-actin filaments increased; (d) the actomyosin MgATPase activity was stimulated by 4- to 10-fold. In the absense of myosin the Dictyostelium extract did not contract, while gelation proceeded normally. During solation of the gel in the absense of myosin: (a) electron microscopy demonstrated that the number of free, recognizable F- actin filaments increased; (b) solation-dependent contraction of the extract and the Ca++-stimulated MgATPase activity were reconstituted by adding puried Dictyostelium myosin. Actin purified from the Dictyostelium extract did not gel (at 2 mg/ml), while low concentrations of actin (0.7-2 mg/ml) that contained several contaminating components underwent rapid Ca++ regulated gelation. These results indicated : (a) gelation in Dictyostelium extracts involves a specific Ca++-sensitive interaction between actin and several other components; (b) myosin is an absolute requirement for contraction of the extract; (c) actin-myosin interactions capable of producing force for movement are prevented in the gel, while solation of the gel by either physical or chemical means results in the release of F-actin capable of interaction with myosin and subsequent contraction. The effectiveness of physical agents in producting contraction suggests that the regulation of contraction by the gel is structural in nature.     

Detection of antibodies in Brugia pahangi-infected cats by counter immunoelectrophoresis, indirect fluorescent antibody test and enzyme-linked immunosorbent assay

In cats infected with Brugia pahangi, antibodies first appeared against the larvae (L3), then against the adults (L5) and the microfilariae (mf). Homologous antigens were better than antigens prepared from heterologous species (Dirofilaria immitis, Dipetalonema viteae, Litomosoides carinii and Onchocerca gutturosa) in detecting antibodies to B. pahangi in the infected cats by indirect fluorescent antibody test (IFAT). Metabolic products of L5, but not L3 or mf, of B. pahangi were antigenic and were used in the enzyme-linked immunosorbent assay (ELISA) for detection of antibodies. Using various homologous antigens, IFAT was found to be more sensitive than counter immunoelectrophoresis and ELISA in the detection of antibodies in the infected cats. The best antigen was cryosections of L3, with a positivity rate of 81%. However, using L3, L5 and mf antigens in IFAT, a total positivity of 97% was obtained.     

The photoinduced isomerization of bilirubin in cationic detergent solutions.

When bilirubin IX alpha in solution in a buffered aqueous cationic detergent near neutral pH is irradiated with visible light, a rapid equilibrium with bilirubin III alpha and XIII alpha is set up. Little isomerization can be detected under comparable conditions in anionic or neutral detergents. The rapid disproportionation of bilirubin monoglucuronide into unconjugated bilirubin and bilirubin diglucuronide also takes place on irradiation in a solution of a cationic detergent.