cAMP-dependent protein kinase: crystallographic insights into substrate recognition and phosphotransfer.

The crystal structure of ternary and binary substrate complexes of the catalytic subunit of cAMP-dependent protein kinase has been refined at 2.2 and 2.25 A resolution, respectively. The ternary complex contains ADP and a 20-residue substrate peptide, whereas the binary complex contains the phosphorylated substrate peptide. These 2 structures were refined to crystallographic R-factors of 17.5 and 18.1%, respectively. In the ternary complex, the hydroxyl oxygen OG of the serine at the P-site is 2.7 A from the OD1 atom of Asp 166. This is the first crystallographic evidence showing the direct interaction of this invariant carboxylate with a peptide substrate, and supports the predicted role of Asp 166 as a catalytic base and as an agent to position the serine -OH for nucleophilic attack. A comparison of the substrate and inhibitor ternary complexes places the hydroxyl oxygen of the serine 2.7 A from the gamma-phosphate of ATP and supports a direct in-line mechanism for phosphotransfer. In the binary complex, the phosphate on the Ser interacts directly with the epsilon N of Lys 168, another conserved residue. In the ternary complex containing ATP and the inhibitor peptide, Lys 168 interacts electrostatically with the gamma-phosphate of ATP (Zheng J, Knighton DR, Ten Eyck LF, Karlsson R, Xuong NH, Taylor SS, Sowadski JM, 1993, Biochemistry 32:2154-2161). Thus, Lys 168 remains closely associated with the phosphate in both complexes. A comparison of this binary complex structure with the recently solved structure of the ternary complex containing ATP and inhibitor peptide also reveals that the phosphate atom traverses a distance of about 1.5 A following nucleophilic attack by serine and transfer to the peptide. No major conformational changes of active site residues are seen when the substrate and product complexes are compared, although the binary complex with the phosphopeptide reveals localized changes in conformation in the region corresponding to the glycine-rich loop. The high B-factors for this loop support the conclusion that this structural motif is a highly mobile segment of the protein.     

Annual variation in fat storage by a migrant warbler overwintering in the Indian tropics

1. We studied fat storage in a population of greenish leaf warblers ( Phylloscopus trochiloides ) in southern India over four winters (1993–97). This species breeds in temperate regions and overwinters in India from October to April.
2. Diurnal variation in fat scores was comparable to that seen among temperate wintering passerines. Seasonal variation was slight, except for premigratory fattening. There was significant annual variation: in drier winters, which were also winters of low food supplies, fat scores were higher.
3. Energy metabolized overnight is unlikely to vary across winters, and annual variation in fat scores is considered a response to uncertainty of food intake on a given day. Fat scores varied inversely with short-term rainfall, which drives the abundance of arthropod prey.
4. Annual variation in fat scores was not accompanied by changes in total body mass. This suggests that protein reserves were being compromised by increased fat deposition in dry years and offers an explanation for the observed delay in moult during drier winters. These results suggest that strategies for maximizing short-term probability of survival translate into future fitness costs, and may shape long-term life-history strategies through simple physiological processes.     

Elicitation of thiophene production by cultured hairy roots of Tagetes patula

Hairy roots of Tagetes patula were initiated by infecting the seedlings with Agrobacterium rhizogenes. The hairy roots were grown in liquid medium MS (Murashige and Skoog 1962) supplemented with sucrose. The roots were treated with three different elicitors obtained from mycelial culture of Aspergillus niger, Rhizopus oligosporus and Pencillium notatum. Accumulation of biomass and the production of thiophenes were studied over a period of six weeks in culture. The HPLC separation profile of the thiophenes indicated the presence of several structurally different thiophenes. α-terthienyl being predominent. Maximum production of thiophene was recorded at the end of the fourth week in culture with a content of 0.138 % (w/w on dry weight basis). Treatment of hairy roots with mycelial extract of Aspergillus niger (1.5 % v/v) elicited an increase in thiophene content by 1.6 folds over the control.     

Facile exchange of glycosyl S,S-acetals to their O,O-acetals and preparation of glycofuranosides from acyclic glycosyl S,S-acetals under metal-free reaction conditions in the presence of 1,3-dibromo-5,5-dimethylhydantoin

Exchange of acyclic glycosyl dithioacetals to their O,O-acetals has been achieved by a generalized reaction protocol mediated by 1,3-dibromo-5,5-dimethylhydantoin under mild, metal-free and neutral conditions. This methodology has been extended to the synthesis of alkyl glycofuranosides.     

HClO4-SiO2 catalyzed per-O-acetylation of carbohydrates

An efficient per-O-acetylation of carbohydrates catalyzed by HClO4-SiO2 is reported using a stoichiometric quantity of acetic anhydride avoiding the use of pyridine and excess acetic anhydride under solvent-free conditions.     

<Emphasis Type="Italic">Macaca munzala</Emphasis>: A New Species from Western Arunachal Pradesh,Northeastern India<Superscript>*</Superscript>

Macaca, comprising 20 well-characterized species, represents the largest and one of the most ecologically and socially diverse of all the nonhuman primate genera. We report the discovery of a macaque that is new to science from the high altitudes of western Arunachal Pradesh, a biodiversity-rich state in northeastern India. We propose the scientific name Macaca munzala and the vernacular name Arunachal macaque for the species. It shares morphological characteristics independently with the Assamese macaque (Macaca assamensis) and with the Tibetan macaque M. thibetana; like them, it appears to belong to the sinica species-group of the genus. However, the species is distinctive in relative tail length, which is intermediate between those of Tibetan and Western Assamese macaques, the subspecies with which it is sympatric. It is also unique in its altitudinal distribution, occurring largely at altitudes between 2000 and 3500 m. We provide a morphological characterization of the species, report preliminary data on its field biology and discuss possible taxonomic identity in relation to the other closely-related species of Macaca.^*This paper is dedicated to Dr. A. J. T. Johnsingh for his immense contributions to the study and conservation of India’s wildlife and for being an inspiration to a whole generation of students.     

Comparison of 16S rRNA gene sequences of genus <Emphasis Type="Italic">Methanobrevibacter</Emphasis>

Background  

The phylogeny of the genus Methanobrevibacter was established almost 25 years ago on the basis of the similarities of the 16S rRNA oligonucleotide catalogs. Since then, many 16S rRNA gene sequences of newly isolated strains or clones representing the genus Methanobrevibacter have been deposited. We tried to reorganize the 16S rRNA gene sequences of this genus and revise the taxonomic affiliation of the isolates and clones representing the genus Methanobrevibacter.     

Trans expression of a Plasmodium falciparum histidine-rich protein II (HRPII) reveals sorting of soluble proteins in the periphery of the host erythrocyte and disrupts transport to the malarial food vacuole

The heme polymer hemozoin is produced in the food vacuole (fv) of the parasite after hemoglobin proteolysis and is the target of the drug chloroquine. A candidate heme polymerase, the histidine-rich protein II (HRPII), is proposed to be delivered to the fv by ingestion of the infected-red cell cytoplasm. Here we show that 97% of endogenous Plasmodium falciparum (Pf) HRPII (PfHRPII) is secreted as soluble protein in the periphery of the red cell and avoids endocytosis by the parasite, and 3% remains membrane-bound within the parasite. Transfected cells release 90% of a soluble transgene PfHRPIImyc into the red cell periphery and contain 10% membrane bound within the parasite. Yet these cells show a minor reduction in hemozoin production and IC(50) for chloroquine. They also show decreased transport of resident fv enzyme PfPlasmepsin I, the endoplasmic reticulum (ER) marker PfBiP, and parasite-associated HRPII to fvs. Instead, all three proteins accumulate in the ER, although there is no defect in protein export from the parasite. The data suggest that novel mechanisms of sorting (i) soluble antigens like HRPII in the red cell cytoplasm and (ii) fv-bound membrane complexes in the ER regulate parasite digestive processes.     

Alcohol as a Risk Factor for Cancer Burden: A Review

Alcohol is eliminated from the body by various metabolic mechanisms. The primary enzymes in such mechanism involved are alcohol dehydrogenase, aldehyde dehydrogenase, cytochrome P450 2E1, and catalase. Variations in the genes for these enzymes have been found to influence alcohol consumption. The consequences of alcohol metabolism include oxygen deficits (i.e., hypoxia) in the liver, resulting in the formation of harmful compounds (i.e., adducts) and highly reactive oxygen-containing molecules (i.e., reactive oxygen species) that can damage cell components. Approximately, worldwide 3.6 % of cancers derive from chronic alcohol drinking, including those of the upper aerodigestive tract, the liver, the colorectum and the breast. Although the mechanisms for alcohol-associated carcinogenesis are not completely understood, recent findings have focused on acetaldehyde, the first and most toxic ethanol metabolite, as a cancer-causing agent. Alcohol-related carcinogenesis may aggravate due to other factors such as smoking and being triggered by genetic susceptibility. Besides, the role of genetic polymorphisms of the alcohol-metabolizing enzymes could not be ruled out.     

Chromosome measurements on an XXp+ male

Summary Measurements carried out on an XX male show that there is a significant difference between the lengths of the short arm of the 2 X chromosomes of this patient and that the short arm of the longer X is also significantly different from that of the X chromosomes derived from normal individuals. The difference lies specifically in the size of the terminal band of the short arm. These results are consistent with the X-Y interchange hypothesis of Ferguson-Smith.