A translocation associated, loss-of-function mutation in the nitrogen metabolite repression regulatory gene of Aspergillus nidulans can revert intracistronically

Summary The areA ^r -18 mutation is a loss-of-function mutation in areA, the positive acting regulatory gene mediating nitrogen metabolite repression in Aspergillus nidulans. It results from a reciprocal translocation which splits the coding region into 5 and 3 moieties. Surprisingly, we have selected rare intracistronic revertants of areA ^r -18. From crosses heterozygous for areA ^r -18 revertant alleles, duplication-deficiency progeny containing two copies of a substantial portion of chromosome IV but lacking part of chromosome III, including the 5 moiety of areA, have been obtained. For all four revertants analysed genetically, growth properties of these duplication-deficiency strains indicate that the reversion events involve the 3 portion of areA and that the 5 portion of areA is unnecessary for the revertant phenotype. This conclusion was directly confirmed for one revertant using Southern blotting. As all four reversion events involve additional chromosomal rearrangements, they probably fuse functional promoters, ribosome binding sites and in frame initiation codons to the 3 portion of the gene. In the course of characterisation of these mutations, new mapping data for a large region of chromosome IV have been generated, and a new reciprocal translocation activating the cryptic regulatory gene areB, whose product can substitute for that of areA, has been identified.     

Effects of NaCl on Metabolic Heat Evolution Rates by Barley Roots

The effect of salinity stress on metabolic heat output of barley (Hordeum vulgare L.) root tips was measured by isothermal microcalorimetry. Several varieties differing in tolerance to salinity were compared and differences quantified. Two levels of inhibition by increasing salt were found. Following the transition from the initial rate to the first level, inhibition remained at about 50% with further increases in salt concentration up to 150 millimolar. The concentration of salt required to inhibit to this level was cultivar dependent. At higher concentrations (>150 millimolar) of salt, metabolism was further decreased. This decrease was not cultivar dependent. The decreased rate of metabolic heat output at the first transition could be correlated with decreases in uptake of NO₃⁻, NH₄⁺, and Pi that occurred as the salt concentration was increased. The high degree of dependence of the inhibition of metabolic heat output on NaCl concentration points to a highly cooperative reaction responsible for the general inhibition of metabolism and nutrient uptake. The time required to attain the first level of salt inhibition is less than 20 minutes. Inhibition of root tips was not reversible by washing with salt free solutions. In addition to revealing these features of salt inhibition, isothermal microcalorimetry is a promising method for convenient and rapid determination of varietal differences in response to increasing salinity.     

Reevaluation of the amino acid sequence of porcine follitropin

We have reevaluated the sequence of porcine follicle-stimulating hormone (pFSH) with more recent protein-sequencing methodology. This has led to revision of the earlier proposed sequence. As with almost all reported gonadotropin -subunits, NH₂-terminal heterogeneity was found in the porcine FSH -subunit (FSH), starting with residue Phe (1), Asp (3), Gly (4), or Thr (7). In the -subunit, there were found to be at least two molecular species, starting with residue Asn (1) (minor 20%) or Cys (3) (major 80%) as NH₂-terminal and ending at residue Glu (108) as COOH-terminal. The net effect of the present revisions is to increase the homology of pFSH with other reported follitropin sequences. Apparent differences in the half-cystine placements in a previous proposal for pFSH compared with other species of FSH are no longer tenable. The half-cystine placements thus remain a constant structural feature throughout the gonadotropin hormones (choriogonadotropin, follitropin, and lutropin).     

Regulation of expression of a sheep metallothionein 1a-sheep growth hormone fusion gene in transgenic mice.

Transgenic mice containing a sheep metallothionein 1a-sheep growth hormone fusion gene exhibited low, tissue-specific basal levels of transgene mRNA expression, resulting in slightly elevated levels of circulating growth hormone that did not lead to a detectable increase in growth. After zinc stimulation, high levels of transgene mRNA expression were induced in a number of tissues; these levels correlated with increased levels of circulating growth hormone, resulting in growth increases of up to 1.5 times the levels of controls and unstimulated transgenic mice. After removal of the zinc stimulus, transgene expression and circulating growth hormone concentrations returned to basal levels. Additional evidence from the pattern of developmental expression of the transgene suggests that zinc is the main regulator of this promoter in mice. The demonstrated regulation and low basal level of expression of the sheep metallothionein 1a promoter make it a candidate for use in other mouse transgenic studies and for use in transgenic livestock, in which regulation of expression is essential.     

Isolation and characterization of cDNA clones encoding the 17.9 and 8.1 kDa subunits of Photosystem I from Chlamydomonas reinhardtii

cDNA clones encoding two Photosystem I subunits of Chlamydomonas reinhardtii with apparent molecular masses of 18 and 11 kDa (thylakoid polypeptides 21 and 30; P21 and P30 respectively) were isolated using oligonucleotides, the sequences of which were deduced from the N-terminal amino acid sequences of the proteins. The cDNAs were sequenced and used to probe Southern and Northern blots. The Southern blot analysis indicates that both proteins are encoded by single-copy genes. The mRNA sizes of the two components are 1400 and 740 nucleotides, respectively. Comparison between the open reading frames of the cDNAs and the N-terminal amino acid sequences of the proteins indicates that the molecular masses of the mature proteins are 17.9 (P21) and 8.1 kDa (P30). Analysis of the deduced protein sequences predicts that both subunits are extrinsic membrane proteins with net positive charges. The amino acid sequences of the transit peptides suggest that P21 and P30 are routed towards the lumenal and stromal sides of the thylakoid membranes, respectively.Abbreviations OEE1, 2 and 3 oxygen evolution enhancer proteins 1, 2 and 3 - Rubisco ribulose bisphosphate carboxylase/oxygenase - PS photosystem - P21 and P30 C. reinhardtii thylakoid polypeptides 21 and 30     

The glue protein of ribbed mussels (Geukensia demissa): a natural adhesive with some features of collagen

Summary The Atlantic ribbed musselGeukensia (Modiolus)demissa attaches itself to the roots of cord grass and other hard objects in tidal salt marshes by spinning adhesive byssal threads. The precursor of a protein apparently present in the adhesive plaques of the threads was isolated in quantity from the foot of the mussel. The protein has an apparent molecular weight of 130000, a pI of 8.1, and contains a high proportion of Gly, Glu/Gln, Lys and 3,4-dihydroxyphenyl-l-alanine (DOPA). Sequence of tryptic peptides suggests a pattern of repeated motifs, such as: Gly-DOPA-Lys, and X-Gly-DOPA-Y-Z-Gly-DOPA/Tyr-Lys, where X is Thr or Ala in octapeptides and Gln-Thr in nonapeptides. Y is variable, but more often than not hydrophobic; and Z is frequently Pro or 4-trans-hydroxyproline (Hyp). The presence of Pro-Gly and Hyp-Gly sequences of -hydroxylysine in the protein is reminiscent of typical collagens; however, the protein is not labile to clostridial collagenase, nor does collagen cross-react with antibodies raised against the mussel protein. Unlike typical collagens, Gly probably occurs only at every 4th or 5th residue in this unusual mussel protein.Abbreviations Anti-Gdfp anti-G. demissa foot protein - Dopa 3,4-dihydroxyphenylalanine - CTAB cetyltrimethylammonium bromide - HPLC high performance liquid chromatography - PAGE polyacrylamide gel electrophoresis Supported by grants from the National Science Foundation (DMB 8500301) and the Office of Naval Research (N00014-86K-0717)     

Time-Place Learning by Garden Warblers (Sylvia borin): Route or Map?

• 1 Garden warblers are able to learn to go to four different feeding places at different times of day (time-place learning). We investigated whether or not the birds rely on a fixed route by preventing them from entering one of the places at the normal time (blocking experiments). At the end of the blocking period the birds were allowed to visit any of the four feeding places.
• 2 In two such blocking experiments, one in which the blocking period was first thing in the morning (from 06.00–10.00 h), the other in which it was later in the day (from 12.00–16.00 h), there was no subsequent shift in the phase of visiting the places during the rest of the day, apart from a tendency to go to the first place of the day after the morning block. These results suggest that the birds do not rely on following a fixed route, but instead use a time-place map.

     

Characterization of a monoclonal antibody against active pectate lyase from Erwinia carotovora

A monoclonal antibody (2E2) produced against pectate lyase from Erwinia carotovora ssp. carotovora reacted with a 41- and a 44-kilodaltion protein on Western blots of concentrated Erwinia culture supernatants resolved by sodium dodecyl sulfate - polyacrylamide gel electrophoresis. It was unequivocally shown that monoclonal 2E2 reacted with an active form of pectate lyase by affinity purifying the antigen with the monoclonal. The affinity-purified antigen was enzymatically active and moved as a single protein band in a nonequilibrium isoelectric focusing gel. Monoclonal 2E2 reacted with the pectate lyases of a diverse range of E. carotovora ssp. carotovora, ssp. atroseptica, and ssp. betavasculorum strains, as well as with one of three strains of E. chrysanthemi. The electrophoretic mobility of the major protein (44 kilodaltons) that reacted with 2E2 was identical within a subspecies but differed among subspecies.     

DNA loop domains in mammalian spermatozoa

The highly condensed and tightly packaged DNA of hamster spermatozoa was found to be organized into topologically constrained DNA loop domains attached at their bases to a nuclear matrix. The loop domains of the sperm nuclei differed from somatic cell loop domains from the same animal in two aspects. Sperm loop domains were 60% smaller than somatic cell loop domains, with an average DNA length of 46±7 kb in sperm as compared with 16±11 kb in brain. Secondly, unlike virtually all somatic cell DNA known which is negatively supercoiled, sperm DNA was devoid of detectable supercoiling. The presence of the loop domain structure in the highly condensed DNA of mammalian spermatozoa suggests that this motif is a fundamental aspect of eukaryotic DNA organization.