Pollen-based biome reconstruction for southern Europe and Africa 18,000 yr bp

Pollen data from 18,000 ¹⁴C yr bp were compiled in order to reconstruct biome distributions at the last glacial maximum in southern Europe and Africa. Biome reconstructions were made using the objective biomization method applied to pollen counts using a complete list of dryland taxa wherever possible. Consistent and major differences from present‐day biomes are shown. Forest and xerophytic woods/scrub were replaced by steppe, both in the Mediterranean region and in southern Africa, except in south‐western Cape Province where fynbos (xerophytic scrub) persisted. Sites in the tropical highlands, characterized today by evergreen forest, were dominated by steppe and/or xerophytic vegetation (cf. today’s Ericaceous belt and Afroalpine grassland) at the last glacial maximum. Available data from the tropical lowlands are sparse but suggest that the modern tropical rain forest was largely replaced by tropical seasonal forest while the modern seasonal or dry forests were encroached on by savanna or steppe. Montane forest elements descended to lower elevations than today.     

Substance P binding sites in the nucleus tractus solitarius of the cat

Substance P binding sites in the nucleus tractus solitarius were visualized with receptor autoradiography using Bolton-Hunter [¹²⁵I]substance P. Substance P binding sites were found to have distinct patterns within the cat nucleus tractus solitarius. The majority of substance P binding sites were present in the medial, intermediate and the peripheral rim of the parvocellular subdivisions. Lower amounts of substance P binding sites were present in the commissural, ventrolateral, interstitial and dorsolateral subdivisions. No substance P binding sites were present in the central region of the parvocellular subdivision or the solitary tract. The localization of substance P binding sites in the nucleus tractus solitarius is very similar to the patterns of substance P immunoreactive fibers previously described for this region. Results of this study add further support for a functional role of substance P in synaptic circuits of the nucleus tractus solitarius.     

Characterization of the glycosylation sites in yeast external invertase. I. N-linked oligosaccharide content of the individual sequons

External invertase is the product of the SUC2 gene of Saccharomyces cerevisiae. The deduced sequence of this enzyme (Taussig, R., and Carlson, M. (1983) Nucleic Acid Res. 11, 1943-1954) reveals it to contain 14 potential N-linked glycosylation sites, or sequons, although only 9-10 appear to be glycosylated (Trimble, R. B., and Maley, F. (1977) J. Biol. Chem. 252, 4409-4412). To determine the location of the glycosylated sequons, external invertase was deglycosylated with endo-beta-acetylglucosaminidase H and its component peptides analyzed by both fast atom bombardment mass spectrometry (FABMS) and classical peptide isolation procedures. By use of the former technique most of the glucosamine-containing sequons could be located and by the latter sufficient amounts of small glucosamine-containing peptides were isolated to enable their quantitation. From the combined FABMS and glucosamine analyses, it was established that eight of the sequons in a subunit of invertase are either completely or almost completely glycosylated, while five others are glycosylated to the extent of about 50% or less. In the case of two overlapping sequons (4 and 5), which include Asn92-Asn93-Thr-Ser, only the first Asn was glycosylated. Thus, all but one of the sequons of external invertase are glycosylated to some extent, giving an appearance of only 9-10 N-linked oligosaccharides/subunit. The sequence identity of both external and internal invertase was verified by FABMS and by peptide sequence analysis. In only one site was an amino acid found to differ from that deduced from the DNA sequence of the SUC2 gene. This occurred at position 390 where a proline was found in place of alanine, which could result from a single base change in the triplet specifying the latter amino acid.     

Thermal Properties of Membrane Lipids from two Cyanobacteria, Anacystis nidulans and Synechococcus sp.

The composition and positional distribution of fatty acids inmonogalactosyldiacylglycerol, digalactosyldiacylglycerol, phosphatidylglyceroland sulphoquinovosyldiacylglycerol from two cyanobacteria, Anacystisnidulans and Synechococcus sp. grown at 25°C have been determinedand compared with measurements of the phase separation temperaturesof the lipids. Only monogalactosyldiacylglycerol in Anacystisand sulphoquinovosyldiacylglycerol in Synechococcus showed phaseseparation temperatures above 0°C. The phase transitiontemperature of a sample of sulphoquinovosyldiacylglycerol containingover 90% of the dihexadecanoyl molecular species has been determinedto be 43°C for the Na⁺ salt and 38°C for the Mg⁺⁺ salt. ^*Deceased. September 14, 1986. (Received June 25, 1986; Accepted August 25, 1986)     

Amplified expression of streptomyces endo-beta-N-acetylglucosaminidase H in Escherichia coli and characterization of the enzyme product

The endo-beta-N-acetylglucosaminidase H (Endo H) gene from Streptomyces plicatus has been cloned into the Escherichia coli plasmid pKC30 (Shimatake, H., and Rosenberg, M. (1981) Nature 272, 128-132), thus placing expression of this gene under control of the strong lambda promoter pL. The construction, pKCE3, which includes a properly positioned E. coli ribosome binding site from the lac operon (Robbins, P.W., Trimble, R. B., Wirth, D.F., Hering, C., Maley, F. Maley, G. F., Das, R., Gibson, B.W., and Biemann, K. (1984) J. Biol. Chem. 259, 7577-7583), was used to transform an E. coli strain lysogenic for a lambda prophage containing a temperature-sensitive repressor. By shifting cultures of pKCE3 lysogens to 42 degrees C, the production of Endo H commenced and was linear for about 1 h. Enzyme yields were amplified 150-fold above those obtained from comparable cultures of S. plicatus and represented 3 to 4% of total cellular protein, which enabled purification of Endo H to homogeneity by a rapid fourstep procedure. Although most of the cloned Endo H was secreted into the periplasmic space by E. coli, its 4 kDa leader sequence peptide (Robbins et al. (1984] was only partially removed during processing. As a result the purified pKCE3 Endo H was a heterogeneous population of molecules with an average molecular mass of 31 kDa compared to the 28.9 kDa fully processed product normally secreted by S. plicatus. Despite the residual approximately 2 kDa of leader sequence on the cloned pKCE3 product, there were no detectable differences in either the substrate specificity or the stability characteristics of the enzyme purified from E. coli or from S. plicatus. Of particular value for studies on glycoproteins was the finding that the genetically engineered Endo H was completely free of proteolytic contaminants.