The binding of bis-ANS to the isolated GroEL apical domain fragment induces the formation of a folding intermediate with increased hydrophobic surface not observed in tetradecameric GroEL

The extent of hydrophobic exposure upon bis-ANS binding to the functional apical domain fragment of GroEL, or minichaperone (residues 191-345), was investigated and compared with that of the GroEL tetradecamer. Although a total of seven molecules of bis-ANS bind cooperatively to this minichaperone, most of the hydrophobic sites were induced following initial binding of one to two molecules of probe. From the equilibrium and kinetics studies at low bis-ANS concentrations, it is evident that the native apical domain is converted to an intermediate conformation with increased hydrophobic surfaces. This intermediate binds additional bis-ANS molecules. Tyrosine fluorescence detected denaturation demonstrated that bis-ANS can destabilize the apical domain. The results from (i) bis-ANS titrations, (ii) urea denaturation studies in the presence and absence of bis-ANS, and (iii) intrinsic tyrosine fluorescence studies of the apical domain are consistent with a model in which bis-ANS binds tightly to the intermediate state, relatively weakly to the native state, and little to the denatured state. The results suggest that the conformational changes seen in apical domain fragments are not seen in the intact GroEL oligomer due to restrictions imposed by connections of the apical domain to the intermediate domain and suppression of movement due to quaternary structure.     

Oxalic acid, Fe-reduction activity and oxidative enzymes detected in culture extracts recovered from Pinus taeda wood chips biotreated by Ceriporiopsis subvermispora

Pinus taeda wood chips were treated with the biopulping fungus, Ceriporiopsis subvermispora, under solid-state fermentation for periods varying from 7 to 90 days. Low molecular mass compounds and oxidative enzymes were extracted from biotreated wood samples. Manganese-dependent peroxidase was the main oxidative enzyme on all biodegradation periods. Aqueous extracts from biotreated wood presented decreasing pH values, oxalic acid being the major organic acid secreted by the fungus. Analysis of these extracts by gas chromatography coupled with mass spectrometry (GC/MS) revealed small amounts of fatty acids, several short-chain organic acids (C3–C6) and numerous sugar derivatives. 3-methoxy-4-hydroxy benzaldehyde, 3-methoxy-4-hydroxy benzoic acid, 3,4-dihydroxy benzoic acid and tricarboxy-benzene were also found in the wood extracts. A remarkable characteristic of the wood extracts was a strong Fe³⁺-reducing ability. High Fe³⁺-reducing activity and high catechol concentrations were detected in the wood extracts from the undecayed control. This reducing activity and catechol concentrations decreased during the first 7 days of biodegradation. However, from the seventh day of culturing, catechol derivatives coming from lignin degradation start to accumulate in the cultures and Fe³⁺-reduction activity increased again. The Fe³⁺-reduction activity observed in the wood extracts indicates that Fe²⁺ would be available in solution during the wood decay process. Considering that Fe²⁺ and H₂O₂ (produced by this fungus based on MnP-degradation of oxalate) were present in the wood extracts, at least some extent for degradation reactions based on Fenton-chemistry, similarly to the observed in brown-rot fungi, is supposed to occur during wood decay by C. subvermispora.     

International NeuroAIDS: prospects of HIV-1 associated neurological com-plications

INTRODUCTION AND NEUROEPIDEMIO- LOGY OF HIV/AIDS AIDS was first recognized as a new and distinct clini- cal entity in 1981 [1] and the HIV-1 as their casual agent in 1983 [2]. Since then, the HIV/AIDS epidemic has reached epidemic proportions with a total accumulative number of more than 60 million people, according to the Joint United Nations Programme on HIV/AIDS (UNAIDS) and WHO. The extensive spread of HIV-1 epidemics in Asia was not appreciated in the 1980s,…     

The HSC73 molecular chaperone: involvement in MHC class II antigen presentation.

Heat shock proteins (HSP) are conserved proteins, many of which share the ability for indiscriminate peptide binding and ATPase-coupled peptide release. In this paper, we show that heat shock cognate protein (HSC)73, a constitutively expressed member of the HSP70 family, could be a candidate for chaperone activity within the MHC class II presentation pathway. HSC73 expression in macrophages was shown to overlap with expression of MHC class II; overexpression of HSC73 in stable transfectants of a macrophage line markedly enhanced their presentation of exogenous Ag without affecting presentation of processing independent peptide. Ag from an exogenous source was demonstrated to associate with HSC73 in macrophages, and this association was sensitive to ATP treatment and inhibited by deoxyspergualin, an immunosuppressive agent that has previously been shown to bind specifically to HSC73. Furthermore, deoxyspergualin reduced Ag presentation by macrophages in relation to the amount of HSC73 expressed in these cells. The data are consistent with a potential role for HSC73 in binding and protecting peptides from extensive degradation and/or facilitating the kinetics of peptide transfer to MHC class II molecules.     

Description of the male of Tityus kuryi Louren?o, 1997 and notes about males of Tityus stigmurus (Thorell, 1877) and Tityus serrulatus Lutz & Mello, 1922 (Scorpiones,Buthidae)

The male of Tityus kuryi Lourenço, 1997 is described for the first time. Despite being very similar to the female, the male presents more robust metasomal segments. Additionally, the distribution of the sexual populations of another two species of the T. stigmurus complex is reported herein: T. serrulatus Lutz & Mello, 1922 and T. stigmurus (Thorell, 1877). Males of T. serrulatus were, until now, restricted to the Minas Gerais State (Southwestern region of Brazil), and with new records reported here, its known distribution now encompasses the Northeastern region of Brazil. Males of T. stigmurus were previously recorded only for two municipalities in the State of Bahia, and here we present eight new records for Bahia State and one for Pernambuco State. We present a key to related species of the T. stigmurus complex based on morphology and coloration pattern.     

A new Sphagesaurus (Mesoeucrocodylia: Notosuchia) from the Upper Cretaceous of Monte Alto City (Bauru Group,Brazil), and a revision of the Sphagesauridae

Oxygen consumption and ammonia excretion rates were assessed for Terebratulina retusa (L.) held under 3 different regimes of temperature and food availability. These were: 5.6?C, no food (cold, starved); 5.8?C, food present (cold, fed) and 10.7?C food present (warm, fed), which simulated winter conditions, summer conditions and an intermediate treatment. Regressions of oxygen consumption on ash‐free dry weight (AFDW) had slopes which were not significantly different from each other and ranged from 0.953 to 0.999. A common slope of 0.976 was calculated and intercepts based on the common slope used to compare oxygen consumption in each treatment. The rise from cold, starved conditions to warm, fed was 24.5 per cent and this was significant (P < 0.05). Other differences were not significant (P > 0.05) but the cold, fed result was 12.6 per cent higher than cold, starved. Therefore feeding and temperature probably account for equivalent proportions of the rise in metabolism from winter to summer. Ammonia production data were much more variable. Excretion rates of a 50 mg AFDW individual (in ng‐at NH₃‐N.h^‐1) were as follows: cold, starved: 30.2 cold, fed: 7.1; and warm, fed: 22.9. Oxygen to nitrogen (O:N) ratios reflected these results. Mean O:N ratios were: cold, starved: 8.0; cold, fed: 42.4; warm, fed: 16.3. This shows that the simulated winter group relied heavily on protein to fuel their metabolism, the simulated summer group were less dependent on protein and the intermediate group probably used lipids and carbohydrates to fuel metabolic demands. This possibly reflected a trade off between food supply and increased metabolism from treatment to treatment, demonstrating a flexibility which could have been a contributing factor in the ecological tolerance and geological longevity of some brachiopods.