Preliminary crystallographic analysis of a proteolytically modified form of E. coli single stranded DNA binding protein

A proteolytically modified form of the Escherichia coli single-stranded DNA-Binding protein (SSB) has been crystallized from 15% saturated sodium citrate. Crystals as large as 1.0 mm x 0.3 mm x 0.2 mm were obtained and these diffract beyond 3A resolution. X-ray photographic analysis demonstrated a rhombohedral unit cell of space group R3 with an equivalent triple centered hexagonal unit cell having dimensions of a = b = 62.9A and c = 264.3A. These crystals were judged to be adequate for a three dimensional structure determination.     

Regulation of apolipoprotein E synthesis and mRNA by diet and hormones

Rats were fasted or fasted and refed simple purified diets so the effects of individual carbohydrates or fats could be studied. Freshly isolated hepatocytes from these animals were used to measure both apoE synthesis and mRNA levels so any changes in apoE synthesis that might occur without changes in its mRNA could be detected. Some of these experiments were done with both sexes. Both fasting and fasting and refeeding a 60% glucose fat-free diet significantly increased spoE synthesis. However, cyclic AMP is not likely to rapidly mediate the effect of fasting since dibutyryl cAMP slightly lowered (rather than increased) apoE synthesis and mRNA when injected into rats for 4.5 h. Dietary fat had no effect either in the absence of carbohydrate or when consumption of carbohydrate was constant in pair-fed rats. ApoE mRNA levels remained normal for 4 days in primary hepatocytes cultured in medium that had only amino acids as an energy source. Added hormones or fructose had no significant effect. Thus, only fasting and fasting and refeeding glucose were able to significantly change apoE synthesis or mRNA levels. Synthesis of apoE may be regulated to increase when apoE is secreted with very low density lipoprotein or when apoE in secreted high density lipoprotein is needed to acquire cholesteryl esters for the synthesis of bile salts and acids by liver.     

Reaction on alternating GC oligonucleotide templates

Summary The condensation reactions of activated nucleotides, ImpN or 2-MeImpN, with the selfcomplementary ribo-octanucleotide GCGCGCGC or with the partially self-complementary heptanucleotide GCGCGCG were studied. The templatedirected reaction of 2-meImpC with the heptamer yields the 3–5 octamer as the main product. All other reactions yield 2–5-linked octamers and pyrophosphates as major products. Surprisingly, 2-MeImpG facilitates the reaction of 2-MeImpC with the heptamer.Procedures for the analysis by gel electrophoresis of the oligomeric products obtained in reactions of this kind are described.     

Genetic structure of Glycine canescens,a perennial relative of soybean

Summary Allozyme variation as detected by starch gel electrophoresis was used to assess the extent and spatial organization of genetic variation across the entire range of Glycine canescens sensu lato. Eleven enzyme systems were assayed in 116 accessions of this taxon and 102 alleles were detected at a total of 31 loci. Eighty-one percent of loci were polymorphic. Most of this variation occurred between and very little within accessions. Three major groupings were detected. These groupings (groups 1, 2, and 3) also differed with respect to mean seed size and their geographic distribution. A further ten accessions stood out from these distinct groups. These accessions were most closely related to group 3 but were variable among themselves. In general, they were collected from highly dissected terrain, often in the remote interior of the continent. A final group of 18 problematic accessions (group X), originally tentatively identified as G. canescens on morphological grounds, was shown to be isozymically distinct from this species and was reclassified as one form of the polytypic species G. clandestina.