Isolation and characterization of the iron-containing superoxide dismutase of Methanobacterium bryantii

Methanobacterium bryantii contains a single electrophoretically discernible superoxide dismutase, which constitutes 0.4% of the extractable protein. This enzyme has been purified to electrophoretic and ultracentrifugal homogeneity. It appears to be a tetramer. The subunits were tenaciously, but noncovalently bonded and were of identical size. The molecular weight of the enzyme was found to be 91,000 ± 2000. The specific activity of this enzyme was identical to that previously noted for the corresponding enzyme from Escherichia coli. The enzyme contained 2.7 atoms of Fe, 1.7 atoms of Zn, and less than 0.2 atoms Mn per tetramer. Its amino acid composition placed this enzyme with the other Mn- and Fe-containing superoxide dismutases. The M. bryantii enzyme was also similar to previously described Fe-containing superoxide dismutases in its optical and electron paramagnetic resonance spectra and in its susceptibility to inactivation by H₂O₂. The M. bryantii enzyme was ininhibited by N₃^?, but was less sensitive towards this inhibitor than other iron-containing superoxide dismutases.     

A novel 3-0 sulfatase from human urine acting on methyl-2-deoxy-2-sulfamino-α-D-glucopyranoside 3-sulfate

Human urine contains a novel sulfatase which is specific for the 3-0 sulfate ester of sulfaminoglucopyranoside 3-sulfate. Of the three isomeric sulfamate derivatives, 3,4 and 6-0 sulfate esters, only the 3-0 ester is hydrolyzed. Enzymatic activity requires that the amino group be sulfated; sulfate is not released if the amino group is free or acetylated. The enzyme has been purified 70-fold. It has a pH optimum of 6.3 and is inhibited by inorganic sulfate and phosphate. The specificity of this enzyme suggests that a 3-0 sulfated glucosamine moiety may have a role in the physiological activity of heparin or heparan sulfate.     

Effect of Chemically Modified 70S RNA from Avian Myeloblastosis Virus (AMV) upon the Activity of AMV DNA Polymerase

Adenine residues of 70S avian myeloblastosis virus (AMV) RNA are modified when reacted with chloroacetaldehyde. This modification introduces characteristic fluorescent epsilon-adenosine (epsilonA) probes which were used to monitor the reaction. Under suitable conditions, modified 70S(epsilonA) RNA was maintained intact and was inactive as a template for the AMV DNA polymerase. Furthermore, it inhibited the reaction catalyzed by AMV polymerase when 70S RNA was used as template-primer and had no effect on the two tested bacterial polymerases. Protection against the 70S (epsilonA) RNA inhibition was observed when 70S RNA was primed with oligo(dT) indicating preference of the polymerase for the oligo(dT) primed regions.     

Purification and functional characterization of integrin alpha v beta 5. An adhesion receptor for vitronectin.

We have purified a novel member of the integrin gene family from placenta that serves as a vitronectin receptor. This integrin is composed of the alpha v subunit and a beta subunit that we designate beta 5. Purification was accomplished by immunodepleting a placental extract of integrin alpha v beta 3, allowing us to purify alpha v beta 5 from the remaining extract by monoclonal antibody affinity chromatography on LM 142-Sepharose, which binds to the alpha v subunit. Purification to homogeneity was subsequently achieved by affinity chromatography on wheat germ lectin-Sepharose. Western blot analysis with antibodies raised against alpha v beta 5 and alpha v beta 3 demonstrated that beta 3 and beta 5 were distinct but confirmed that the alpha subunit of the two integrins were immunologically identical. Similarly, antibodies that bind beta 3 proximal to the ligand-binding site failed to react with beta 5, indicating an architectural difference at the ligand-binding site of these related integrins. This structural difference apparently results in a functional distinction, since purified alpha v beta 3 bound to vitronectin, fibrinogen, von Willebrand factor, and fibronectin, whereas integrin alpha v beta 5 bound preferentially to vitronectin. Finally, we demonstrate by three criteria that beta 5 and beta x, the latter of which was identified in lung carcinoma cells (Cheresh, D. A., Smith, J. W., Cooper, H. M., and Quaranta, V. (1989) Cell 57, 59-69), are identical. First, peptide maps of beta x and beta 5 are identical. Secondly, polyclonal antibodies raised against alpha v beta 5 immunoprecipitate both beta 5 and beta x, and finally, the amino-terminal amino acid sequences of beta x and beta 5 are identical.     

Individual performance in relation to cytonuclear discordance in a northern contact zone between long‐toed salamander (Ambystoma macrodactylum) lineages

Cytonuclear discordance in contact zones between related lineages is common, with mitochondrial clines often being displaced from clines in nuclear allele frequency. Proposed explanations for such a pattern include adaptive introgression of mtDNA or a neutral wake of mtDNA being left behind following hybrid zone movement. However, studies investigating these hypotheses are rare. Our previous survey of genetic variation in the long‐toed salamander (Ambystoma macrodactylum) highlighted a potential case of cytonuclear discordance between two lineages in western Canada. Here, we use additional markers and samples to clarify the extent of this discordance. We simultaneously assess the feeding performance of individuals in a common environment to test for an association between mitotype and individual performance. The genetic results confirm a general pattern of cytonuclear discordance in the focal region. However, we also observed more limited introgression of a diagnostic nuclear marker. Intriguingly, although there were differences in individual performance associated with the transition between mitotypes, these differences were not fully explained by mitotype. Instead, the lowest performance was observed in individuals demonstrating the greatest mismatch between mtDNA and all nuclear markers, suggesting the potential for cytonuclear incompatibilities to be acting. These results highlight the complexity of understanding the causes and consequences of mtDNA introgression and cytonuclear discordance in contact zones.     

Artificial selection on larval growth curves in Tribolium: correlated responses and constraints

Body size is often constrained from evolving. Although artificial selection on body size in insects frequently results in a sizable response, these responses usually bear fitness costs. Further, these experiments tend to select only on size at one landmark age, rather than selecting for patterns of growth over the whole larval life stage. To address whether constraints may be caused by larval growth patterns rather than final size, we implemented a function‐valued (FV) trait method of selection, in which entire larval growth curves from Tribolium were artificially selected. The selection gradient function used was previously predicted to give the maximal response and was implemented using a novel selection index in the FV framework. Results indicated a significant response after one generation of selection, but no response in subsequent generations. Correlated responses included increased mortality, increased critical weight, and decreased development time (DT). The lack of response in size and development time after the first generation was likely caused by increased mortality suffered in selected lines; we demonstrated that the selection criterion caused both increased body size and increased mortality. We conclude that artificial selection on continuous traits using FV methods is very efficient and that the constraint of body size evolution is likely caused by a suite of trade‐offs with other traits.     

Complex organization of zein genes in maize

We have examined the fragments of maize nuclear DNA that are homologous to three cloned cDNAs prepared from zein mRNA. Southern blots of high molecular weight ( > 40 kb) maize nuclear DNA cleaved with BamHI, HindIII or EcoRI were hybridized to three zein cDNA plasmid probes. Multiple restriction fragments in a wide range of size classes were observed to hybridize with all three probes. Our results indicate the occurrence of families of genes in the maize genome that are related by their sequences to a given zein mRNA sequence.