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.     

Single channel kinetics of a glutamate receptor.

The glutamate receptor-channel of locust muscle membrane was studied using the patch-clamp technique. Muscles were pretreated with concanavalin A to block receptor-channel desensitization, thus facilitating analysis of receptor-channel gating kinetics. Single channel kinetics were analyzed to aid in identification of the molecular basis of channel gating. Channel dwell-time distributions and dwell-time autocorrelation functions were calculated from single channel data recorded in the precence of 10-4M glutamate. Analysis of the dwell time distributions in terms of mixtures of exponential functions revealed there to be at least three open states of the receptor-channel and at least four closed states. Autocorrelation function analysis showed there to be at least three pathways linking the open states with the closed. This results in a minimal scheme for gating of the glutamate receptor-channel, which is suggestive of allosteric models of receptor-channel gating.     

New and noteworthy South American species of Agalinis (Scrophulariaceae)

Agalinis bandeirensis is a Brazilian species distinguished by linear bracts, short pedicels, and villous stamens.Agalinis ramulifera, from southern Brazil, is distinguished by many, short, leafy branches and small flowers.Agalinis linarioides subsp.rojasi, from Paraguay, is distinguished by paniculate inflorescences, short calyx lobes, and broad corollas.Gerardia bangii, G. digitalis, andG. meyeniana are recognized as species ofAgalinis and appropriate transfers are made.     

Cardiovascular actions of adenosines, but not adenosine receptors, differ in rat and guinea pig

This study compared the structure-activity relationships of 16 analogues at the A1 and A2 adenosine receptors (A1AR, A2AR) of rat and guinea pig. Radioligand binding studies revealed no marked differences in the affinities of each analogue at the A1AR of brain cortex or the A2AR of brain striatum. Bioassay employing Langendorff heart preparations showed that the guinea pig is more sensitive than the rat to A1AR-mediated slowing of conduction through the atrioventricular node and, in some instances, to A2AR-mediated coronary vasodilation. That difference could reflect factors such as receptor density or efficacy of coupling to effector systems.     

Metabolism of sulfur-containing amino acids by pregnant merino ewes

The availability and utilization of cystine and methionine were measured in single-bearing Merino ewes on three occasions, approximately 90, 110 and 130 days after mating, and the effects on these traits of sulfur amino acids (SAA) infused into the abomasum were also measured. Two levels of SAA were infused containing 0.5 or 1.0 g day-1 organic sulfur with DL-methionine contributing two-thirds and L-cystine one-third of the supplementary sulfur. The quantity of the diet offered was increased at each occasion so as to maintain maternal liveweight. The rates of irreversible loss of both cystine and methionine from plasma increased as pregnancy advanced, but the ratios between the rates of irreversible loss and intake of digestible organic matter (DOMI) did not vary with stage of pregnancy. The average daily rates of irreversible loss of cystine and methionine by the ewes consuming the diet alone were 13.6 and 119 mmol kg-1 DOMI respectively. The average rates of irreversible loss of methionine (Im, mmol h-1) and of cystine (Ic, mmol h-1) were both linearly (P less than 0.05) related to the rate of infusion of organic sulfur into the abomasum (s, g day-1): Im = 2.44 (+/- 0.33) s + 1.28 (+/- 0.13); and Ic = 0.16 (+/- 0.02) s + 0.30 (+/- 0.01). Five per cent of the rate of irreversible loss of cystine arose from trans-sulfuration of methionine by ewes consuming the ration only, but greater percentages (14 and 22%) were observed when the ration was supplemented with SAA (P less than 0.05). These transfer quotients were not influenced by stage of pregnancy. The stage of pregnancy did not influence the concentration of cystine or methionine in the plasma, but the abomasal infusions of SAA significantly increased the concentration of both SAA. The ewes consuming the basal diet were in positive balance for both nitrogen and sulfur. The retention of nitrogen did not vary with stage of pregnancy (average (s.e.), 5.8 (0.9) g day-1), but that of sulfur increased from 0.6 to 1.0 and 1.3 g day-1 in periods 1, 2 and 3, respectively (P less than 0.05). The retentions of nitrogen (N, g day-1) and of sulfur (S, g day-1) were linearly and significantly related to the rate of infusion of organic sulfur into the abomasum (s, g day-1): N = 2.7 (+/- 0.7)s + 4.4 (+/- 0.3); and S = 0.49 (+/- 0.03)s + 0.72 (+/- 0.01).(ABSTRACT TRUNCATED AT 400 WORDS)     

New species of Aristolochia (Aristolochiaceae) from Peru

Aristolochia fosteri is a new species with unusual branched trichomes collected in Pasco near Oxapampa.Aristolochia hutchisonii is a prostrate species found in Amazonas and Cajamarca that is related toA. weberbaueri.Aristolochia barbouri is a narrow-leaved, herbaceous liana from Madre de Dios.     

Three new species of Elleanthus (Orchidaceae) from Central America

Elleanthus stolonifer andE. tillandsioides are new species in theE. poiformis complex of sectionChloidelyna.Elleanthus lentii is a new species in sectionStachydelyna. Elleanthus stolonifer is widespread in the mountains of Costa Rica and Panama;E. tillandsioides is found only in the lowland forests of southeastern Costa Rica;E. lentii is limited to the Cordillera de Guanacaste of Costa Rica.     

Two new species of Esterhazya (Scrophulariaceae) from Brazil

Barringer, Kerry (Department of Botany, Field Museum of Natural History, Chicago, IL 60605). Two new species of Esterhazya (Scrophulariaceae) from Brazil. Brittonia 37: 195–198. 1985.—Esterhazya petiolata is a distinctive species with ovate, petiolate leaves, spreading brances, and broadly tubular-campanulate flowers. It is known from the Serra Dourada of Goiás. Esterhazya eitenorum has narrow, lanceolate leaves, acute calyx lobes, and purple-pink flowers and is known from the planalto of Mt. Itatiaia.     

Trans splicing of mRNA precursors in vitro

Two exon segments from two separate RNA molecules can be joined in a trans splicing process. In trans splicing reactions, an RNA molecule containing an exon, a 5' splice site, and adjacent intron sequences was mixed with an RNA molecule containing an exon, a 3' splice site, and adjacent intron sequences. The efficiency of trans splicing of these two RNAs increased if the two termini of the intervening sequences were paired in a short RNA duplex. However, trans splicing of two RNA molecules with no significant complementarity was also observed. These results strongly suggest that significant secondary structures within intervening sequences could affect the splicing of flanking exons. Similarly, RNAs that are complementary to segments within the intervening sequences could potentially regulate the selection of splice sites. Finally, some organisms might use trans splicing to distribute a single exon to many different mRNAs.