Identification of the coding region for the putidaredoxin reductase gene from the plasmid of Pseudomonas putida

The first 12 NH₂-terminal amino acids of the Pseudomonas putida putidaredoxin reductase were shown to be Met-Asn-Ala-Asn-Asp-Asn-Val-Val-Ile-Val-Gly-Thr. Comparison of these data with the DNA sequence of the BamHI-HindIII 197-base fragment derived from the PstI 2.2-kb fragment obtained from the P. putida plasmid showed that the putidaredoxin reductase gene was downstream from the cytochrome P-450 gene and the intergenic region had the 24-nucleotide sequence TAAACACATGGGAGTGCGTGCTAA. The Shine-Dalgarno sequence GGAG was detected in this region. The initiating triplet for the reductase gene was GTG, which normally codes for valine, but in the initiating codon position codes for methionine. From the amino acid sequence and X-ray data comparisons with other flavoproteins, what appears to be the AMP binding region of the FAD can be recognized in the NH₂-terminal portion of the reductase involving residues 5–35.This article was presented during the proceedings of the International Conference on Macromolecular Structure and Function, held at the National Defence Medical College, Tokorozawa, Japan, December 1985.     

THE PERMEABILITY OF LIVING CELLS TO DYES AS AFFECTED BY HYDROGEN ION CONCENTRATION

1. An accurate quantitative method of measuring the penetration of dye into the living cell is described. 2. Cresyl blue is unable to penetrate rapidly unless the pH outside the cell is decidedly greater than that inside. The rate of penetration increases with increasing pH. 3. Around pH 9 penetration of the dye is rapid while the reverse is true of exosmosis. At low pH values (5.9) exosmosis is rapid and penetration is very slow.     

Competition for nectar resources does not affect bee foraging tactic constancy

1. Competition alters animal foraging, including promoting the use of alternative resources. It may also impact how animals feed when they are able to handle the same food with more than one tactic. Competition likely impacts both consumers and their resources through its effects on food handling, but this topic has received little attention. 2. Bees often use two tactics for extracting nectar from flowers: they can visit at the flower opening, or rob nectar from holes at the base of flowers. Exploitative competition for nectar is thought to promote nectar robbing. If so, higher competition among floral visitors should reduce constancy to a single foraging tactic as foragers will seek food using all possible tactics. To test this prediction, field observations and two experiments involving bumble bees visiting three montane Colorado plant species (Mertensia ciliata, Linaria vulgaris, Corydalis caseana) were used under various levels of inter- and intra-specific competition for nectar. 3. In general, individual bumble bees remained constant to a single foraging tactic, independent of competition levels. However, bees that visited M. ciliata in field observations decreased their constancy and increased nectar robbing rates as visitation rates by co-visitors increased. 4. While tactic constancy was high overall regardless of competition intensity, this study highlights some intriguing instances in which competition and tactic constancy may be linked. Further studies investigating the cognitive underpinnings of tactic constancy should provide insight on the ways in which animals use alternative foraging tactics to exploit resources.     

Relationship between alpha-helical propensity and formation of the ribonuclease-S complex.

Variant semisynthetic ribonuclease-S complexes were characterized in which the helical glutamic acid 9 residue was replaced by either leucine or glycine. The Leu-9 and Gly-9 synthetic peptides, corresponding otherwise to residues 1 through 15 of bovine pancreatic ribonuclease, were studied with respect to the ability to bind, and generate enzymic activity, with the complementary native protein fragment containing residues 21 through 124 of ribonuclease (RNAase-S-(21–124)). Both the Leu and Gly peptides bind to the RNAase-S-(21–124) to yield complexes with catalytic properties similar to those obtained with the Glu-9-containing peptide of residues 1 through 20 of ribonuclease (RNAase-S-(1–20)). However, whereas the binding affinity of Leu peptide to RNAase-S-(21–124) is only a factor of three less than that for RNAase-S-(1–20), that for Gly peptide is about 20-fold less than that for RNAase-S-(1–20). The stronger binding of Leu than Gly peptide corresponds to the observed propensity of leucine but not glycine for the α-helical conformation in globular proteins.In spite of the weakened affinity of the Gly peptide for RNAase-S-(21–124), it is essentially fully as capable as the Leu-9 and RNAase-S-(1–20) peptides in directing the re-formation of correct disulfide-containing conformation of RNAase-S-(21–124) after disulfide randomization of the latter.