Heme pocket disorder in myoglobin: reversal by acid-induced soft refolding

The protein folding process of heme proteins entails generation of not only a correct global polypeptide structure, but also a correct, functionally competent heme environment. We employed a variety of spectroscopic approaches to probe the structure and dynamics of the heme pocket of a recombinant sperm whale myoglobin. The conformational characteristics were examined by circular dichroism, time-resolved fluorescence spectroscopy, FTIR spectroscopy, and optical absorption spectroscopy in the temperature range 300-20 K. Each of these spectroscopic probes detected modifications confined exclusively to the heme pocket of the expressed myoglobin relative to the native protein. The functional properties were examined by measuring the kinetics of CO binding after flash-photolysis. The kinetics of the expressed myoglobin were more heterogeneous than those of the native protein. Mild acid exposure of the ferric derivative of the recombinant protein resulted in a protein with "nativelike" spectroscopic properties and homogeneous CO binding kinetics. The heme pocket modifications observed in this recombinant myoglobin do not derive from inverted heme. In contrast, when native apomyoglobin is reconstituted with the heme in vitro, the heme pocket disorder could be attributed exclusively to 180 degrees rotation of the bound heme [La Mar, G. N., Toi, H., and Krishnamoorthi, R. (1984) J. Am. Chem. Soc. 106, 6395-6401; Light, W. R., Rohlfs, R. J., Palmer, G., and Olson, J. S. (1987) J. Biol. Chem. 262, 46-52]. We conclude that exposure to low pH decreases the affinity of globin for the heme and allows an extended conformational sampling or "soft refolding" to a nativelike conformation.     

Extended cardiolipin anchorage to cytochrome c: a model for protein–mitochondrial membrane binding

Two models have been proposed to explain the interaction of cytochrome c with cardiolipin (CL) vesicles. In one case, an acyl chain of the phospholipid accommodates into a hydrophobic channel of the protein located close the Asn52 residue, whereas the alternative model considers the insertion of the acyl chain in the region of the Met80-containing loop. In an attempt to clarify which proposal offers a more appropriate explanation of cytochrome c–CL binding, we have undertaken a spectroscopic and kinetic study of the wild type and the Asn52Ile mutant of iso-1-cytochrome c from yeast to investigate the interaction of cytochrome c with CL vesicles, considered here a model for the CL-containing mitochondrial membrane. Replacement of Asn52, an invariant residue located in a small helix segment of the protein, may provide data useful to gain novel information on which region of cytochrome c is involved in the binding reaction with CL vesicles. In agreement with our recent results revealing that two distinct transitions take place in the cytochrome c–CL binding reaction, data obtained here support a model in which two (instead of one, as considered so far) adjacent acyl chains of the liposome are inserted, one at each of the hydrophobic sites, into the same cytochrome c molecule to form the cytochrome c–CL complex.     

Global transcriptional response of pig brain and lung to natural infection by Pseudorabies virus

Background  

Pseudorabies virus (PRV) is an alphaherpesviruses whose native host is pig. PRV infection mainly causes signs of central nervous system disorder in young pigs, and respiratory system diseases in the adult.     

Molecular structure, bioavailability and bioactivity of [Cu(o-phen)2(cnge)](NO3)2.2H2O and [Cu(o-phen)(cnge)(H2O)(NO3)2] complexes

Two Cu(II) complexes with cyanoguanidine (cnge) and o-phenanthroline, [Cu(o-phen)(2)(cnge)](NO(3))(2).2H(2)O (1) and [Cu(o-phen)(cnge)(H(2)O)(NO(3))(2)] (2), have been synthesized using different experimental techniques and characterized by elemental analyses, FTIR, diffuse and UV-vis spectra and EPR and magnetic moment measurements techniques. The crystal structures of both complexes were solved by X-ray diffraction methods. Complex (1) crystallizes in the monoclinic space group C2/c with a=12.621(5), b=31.968(3), c=15.39(1)A, beta=111.68(4) degrees, and Z=8 and complex (2) in the monoclinic space group P2(1)/n with a=10.245(1), b=13.923(2), c=12.391(2)A, beta=98.07(1) degrees, and Z=4. The environments of the copper(II) center are trigonal bipyramidal (TBP) for [Cu(o-phen)(2)(cnge)](2+) and an elongated octahedron for [Cu(o-phen)(cnge)(H(2)O)(NO(3))(2)]. Solution studies have been performed to determine the species distribution. The superoxide dismutase (SOD) activities of both complexes have also been tested in order to determine if these compounds mimic the enzymatic action of the enzyme SOD that protects cells against peroxide radicals.     

Omega-3 and Omega-6 Fatty Acids Act as Inhibitors of the Matrix Metalloproteinase-2 and Matrix Metalloproteinase-9 Activity

Polyunsaturated fatty acids have been reported to play a protective role in a wide range of diseases characterized by an increased metalloproteinases (MMPs) activity. The recent finding that omega-3 and omega-6 fatty acids exert an anti-inflammatory effect in periodontal diseases has stimulated the present study, designed to determine whether such properties derive from a direct inhibitory action of these compounds on the activity of MMPs. To this issue, we investigated the effect exerted by omega-3 and omega-6 fatty acids on the activity of MMP-2 and MMP-9, two enzymes that actively participate to the destruction of the organic matrix of dentin following demineralization operated by bacteria acids. Data obtained (both in vitro and on ex-vivo teeth) reveal that omega-3 and omega-6 fatty acids inhibit the proteolytic activity of MMP-2 and MMP-9, two enzymes present in dentin. This observation is of interest since it assigns to these compounds a key role as MMPs inhibitors, and stimulates further study to better define their therapeutic potentialities in carious decay.     

Sorting of GFP Tagged NtSyr1, an ABA Related Syntaxin

Exocytosis molecular mechanisms in plant cells are not fully understood. The full characterization of molecular determinants, such as SNAREs, for the specificity in vesicles delivery to the plasma membrane should shed some light on these mechanisms. Nicotiana tabacum Syntaxin 1 (NtSyr1 or SYP121) is a SNARE protein required for ABA control of ion channels and appears involved in the exocytosis of exogenous markers.NtSyr1 is mainly localized on the plasma membrane, but when over expressed the protein also appears on endomembranes. Since NtSyr1 is a tail-anchored protein inserted into the target membrane post-translationally, it is not clear whether its initial anchoring site is the ER or the plasma membrane.In this study, we investigated the sorting events of NtSyr1 in vivo using its full-length cDNA or its C-terminal domain, fused to a GFP tag and transiently expressed in protoplasts or in the leaves of Nicotiana tabacum cv. SR1. Five chimeras were produced of which two were useful to investigate the protein sorting within the endomembrane system. One (GFP-H3M) had a dominant negative effect on exocytosis; the other one (SP1-GFP) resulted in a slow targeting to the same localization of the full-length chimera (GFP-SP1). The insertion of signal peptides on SP1-GFP further characterized the insertion site for this protein. Our data indicates that NtSyr1 is firstly anchored on ER membrane and then sorted to plasma membrane.Key Words: syntaxins, SNAREs, GFP tagging, exocytosis, secretion, protoplasts, dominant negative mutant     

Salt-induced formation of the A-state of ferricytochrome c--effect of the anion charge on protein structure

Structural information on partially folded forms is important for a deeper understanding of the folding mechanism(s) and the factors affecting protein stabilization. The non-native compact state of equine cytochrome c stabilized by salts in an acidic environment (pH 2.0-2.2), called the A-state, is considered a suitable model for the molten globule of cytochrome c, as it possesses a native-like alpha-helix conformation but a fluctuating tertiary structure. In this article, we extend our knowledge on anion-induced protein stabilization by determining the effect of anions carrying a double negative charge; unlike monovalent anions (which are thought to exert an 'ionic atmosphere' effect on the macromolecule), divalent anions are thought to bind to the protein at specific surface sites. Our data indicate that divalent anions, in comparison to monovalent ions, have a greater tendency to stabilize the native-like M-Fe(III)-H coordinated state of the protein. The possibility that divalent anions may bind to the protein at the same sites previously identified for polyvalent anions was evaluated. To investigate this issue, the behavior of the K88E, K88E/T89K and K13N mutants was investigated. The data obtained indicate that the mutated residues, which contribute to form the binding sites of polyanions, are important for stabilization of the native conformation; the mutants investigated, in fact, all show an increased amount of the misligated H-Fe(III)-H state and, with respect to wild-type cytochrome c, appear to be less sensitive to the presence of the anion. These residues also modulate the conformation of unfolded cytochrome c, influencing its spin state and the coordination to the prosthetic group.     

Network medicine: linking disorders

The molecular events underlying many human hereditary disorders remain to be discovered despite the significant advances made in molecular biology and genetics in the past years. Given the complexity of cellular systems and the interplay between different functional modules, it is becoming increasingly evident that profound insights into human disease cannot be derived by analyzing single genetic defects. The generation of different types of disease interaction networks has recently emerged as a unifying approach that holds the promise of shedding some light on common pathological mechanisms by placing the single disorders into a larger context. In this review, I summarize the rationale behind these disease networks and different ways of constructing them. Finally, I highlight some of the first results that have been obtained by systematically analyzing the intertwined relationships between human disorders because they suggest that the current disease classification does not always sufficiently reflect biologically and medically relevant disease relationships.     

A dysregulated endocannabinoid-eicosanoid network supports pathogenesis in a mouse model of Alzheimer's disease

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Highlights? Monoacylglycerol lipase (MAGL) is a major contributor to brain arachidonic acid pools ? MAGL mutation decreases neuroinflammation and amyloid β in Alzheimer's disease mouse ? MAGL blockade recapitulates brain prostaglandin and cytokine-lowering effects ? MAGL inhibitors may be a next-generation strategy for combating Alzheimer's disease