Isolation and characterization of an abundant and novel 22-kDa protein (SM22) from chicken gizzard smooth muscle

Chicken gizzard smooth muscle contains a highly abundant protein (SM22) with an apparent Mr on sodium dodecyl sulfate-polyacrylamide electrophoretic gels of 23,000. The ratio of actin:SM22:tropomyosin in this tissue is estimated to be 6.5(+/- 0.8):2.0(+/- 0.2):1.0. At least three isoelectric isoforms are present in ratios of alpha:beta:gamma of 14:5:1 with alpha the most basic and gamma the most acidic. A method for the purification of SM22 and partial separation of its isoforms is described. Amino acid analyses of purified alpha and beta demonstrate the presence of 1 and 2 half-cystines, respectively, and a lower content of basic amino acids in beta. A value of 22,000 for the Mr of alpha estimated by sedimentation equilibrium indicated its presence as a monomer at physiological ionic strengths. Estimates of the translational frictional coefficient (f/fmin) of alpha calculated from its Stokes radius (25.5 A) and Mr were consistent with its existence as a moderately asymmetric globular protein. Calculations based on its far-ultraviolet CD spectrum provided values of 37% alpha-helix, 31% beta-sheet, 5% beta-turn, and 27% random coil. SM22 was shown not to share functional properties with several proteins of similar Mr and isoelectric point such as myokinase, brain 23-kDa protein, and troponin I. We conclude that it is a novel protein not previously isolated or characterized from any tissue.     

Interocular orientation disparity and the stereoscopic perception of slanted surfaces

The orientation threshold for two-dimensional filtered noise stimuli was estimated using forced-choice procedures with both dioptic and dichoptic viewing. In the dioptic case the two patterns were co-rotated. In the dichoptic case the stimuli were counter-rotated to produce an orientation disparity, which yields a percept of slant about the horizontal axis orthogonal to the cyclopean line of sight. Dioptic thresholds increased with the orientation bandwidth of the stimuli. In contrast, dichoptic thresholds were essentially constant across a wide range of conditions. In all cases, dichoptic orientation acuity was much finer than conventional estimates. In a second experiment, the dichoptic threshold was estimated for patterns superimposed on a depth pedestal. Acuity was affected significantly by the presence of the pedestal, and was an inverse function of pedestal amplitude. The results suggest that stereoscopic slant caused by dichoptic counter-rotation arises because of neural processing of the overall pattern of disparities of position produced by counter-rotation, rather than specialised encoding of orientation disparity.     

Bacterial cell membrane hydrolysis by secreted phospholipases A(2): a major physiological role of human group IIa sPLA(2) involving both bacterial cell wall penetration and interfacial catalysis

The ability of human group IIa secreted phospholipase A(2) (human sPLA(2)) to hydrolyse the phospholipid membrane of whole cell suspensions of Gram-positive bacteria is demonstrated in real time using a continuous fluorescence displacement assay. Micrococcus luteus is used as a model system and demonstrates an almost absolute specificity for this human enzyme compared with porcine pancreatic and Naja naja venom sPLA(2)s. This specificity is due to selective penetration of the highly cationic human sPLA(2)50%) phospholipid hydrolysis was observed and this was confirmed by electrospray mass spectrometry that allowed the identification of several molecular species of phosphatidylglycerol as the targets for hydrolysis. However, the bactericidal activity of the human enzyme under these assay conditions was low, highlighting the capacity of the organism to survive a major phospholipid insult. In addition to pure enzyme, the human sPLA(2) activity in tears was demonstrated using M. luteus as substrate. In comparison to M. luteus, cell suspensions of Staphylococcus aureus were highly resistant to hydrolysis by human sPLA(2) as well as to the pancreatic and venom enzymes. Treatment of this organism with the specific cell wall protease lysostaphin resulted in a dramatic enhancement in cell membrane phospholipid hydrolysis by all three sPLA(2)s. Overall, the results highlight the potential of the human sPLA(2) as a selective antimicrobial agent against Gram-positive bacteria in vivo because this enzyme is essentially inactive against mammalian plasma membranes. However, the enzyme will be most effective in combination with other antimicrobial agents that enhance the permeability of the bacterial cell wall and where potentiation of the effectiveness of other antibiotics would be expected.     

Current status of antisense DNA methods in behavioral studies

The antisense DNA method has been used successfully to block the expression of specific genes in vivo in neuronal systems. An increasing number of studies in the last few years have shown that antisense DNA administered directly into the brain can modify various kinds of behaviors. These findings strongly suggest that the antisense DNA method can be used as a powerful tool to study causal relationships between molecular processes in the brain and behavior. In this article we review the current status of the antisense method in behavioral studies and discuss its potentials and problems by focusing on the following four aspects; (i) optimal application paradigms of antisense DNA methods in behavioral studies; (ii) efficiencies of different administration methods of antisense DNA used in behavioral studies; (iii) determination of specificity of behavioral effects of antisense DNA; and (iv) discrepancies between antisense DNA effects on behaviors and those on protein levels of the targeted gene.      

Plasma proteome analysis in HTLV-1-associated myelopathy/tropical spastic paraparesis

Background

A new subgroup of HIV-1, designated Group P, was recently detected in two unrelated patients of Cameroonian origin. HIV-1 Group P phylogenetically clusters with SIVgor suggesting that it is the result of a cross-species transmission from gorillas. Until today, HIV-1 Group P has only been detected in two patients, and its degree of adaptation to the human host is largely unknown. Previous data have shown that pandemic HIV-1 Group M, but not non-pandemic Group O or rare Group N viruses, efficiently antagonize the human orthologue of the restriction factor tetherin (BST-2, HM1.24, CD317) suggesting that primate lentiviruses may have to gain anti-tetherin activity for efficient spread in the human population. Thus far, three SIV/HIV gene products (vpu, nef and env) are known to have the potential to counteract primate tetherin proteins, often in a species-specific manner. Here, we examined how long Group P may have been circulating in humans and determined its capability to antagonize human tetherin as an indicator of adaptation to humans.

Results

Our data suggest that HIV-1 Group P entered the human population between 1845 and 1989. Vpu, Env and Nef proteins from both Group P viruses failed to counteract human or gorilla tetherin to promote efficient release of HIV-1 virions, although both Group P Nef proteins moderately downmodulated gorilla tetherin from the cell surface. Notably, Vpu, Env and Nef alleles from the two HIV-1 P strains were all able to reduce CD4 cell surface expression.

Conclusions

Our analyses of the two reported HIV-1 Group P viruses suggest that zoonosis occurred in the last 170 years and further support that pandemic HIV-1 Group M strains are better adapted to humans than non-pandemic or rare Group O, N and P viruses. The inability to antagonize human tetherin may potentially explain the limited spread of HIV-1 Group P in the human population.     

Lactate dehydrogenase (LDH) gene duplication during chordate evolution: the cDNA sequence of the LDH of the tunicate Styela plicata

L-Lactate dehydrogenase (L-LDH, E.C. 1.1.1.27) is encoded by two or three loci in all vertebrates examined, with the exception of lampreys, which have a single LDH locus. Biochemical characterizations of LDH proteins have suggested that a gene duplication early in vertebrate evolution gave rise to Ldh-A and Ldh-B and that an additional locus, Ldh-C arose in a number of lineages more recently. Although some phylogenetic studies of LDH protein sequences have supported this pattern of gene duplication, others have contradicted it. In particular, a number of studies have suggested that Ldh-C represents the earliest divergence among vertebrate LDHs and that it may have diverged from the other loci well before the origin of vertebrates. Such hypotheses make explicit statements about the relationship of vertebrate and invertebrate LDHs, but to date, no closely related invertebrate LDH sequences have been available for comparison. We have attempted to provide further data on the timing of gene duplications leading to multiple vertebrate LDHs by determining the cDNA sequence of the LDH of the tunicate Styela plicata. Phylogenetic analyses of this and other LDH sequences provide strong support for the duplications giving rise to multiple vertebrate LDHs having occurred after vertebrates diverged from tunicates. The timing of these LDH duplications is consistent with data from a number of other gene families suggesting widespread gene duplication near the origin of vertebrates. With respect to the relationships among vertebrate LDHs, our data are not consistent with previous claims that Ldh-C represented the earliest divergence. However, the precise relationships among some of the main lineages of vertebrate LDHs were not resolved in our analyses.      

Maximal activation of skeletal muscle thin filaments requires both rigor myosin S1 and calcium

The regulation by calcium and rigor-bound myosin-S1 of the rate of acceleration of 2'-deoxy-3'-O-(N-methylanthraniloyl)ADP (mdADP) release from myosin-mdADP-P(i) by skeletal muscle thin filaments (reconstituted from actin-tropomyosin-troponin) was measured using double mixing stopped-flow fluorescence with the nucleotide substrate 2'-deoxy-3'-O-(N-methylanthraniloyl). The predominant mechanism of regulation is the acceleration of product dissociation by a factor of approximately 200 by thin filaments in the fully activated conformation (bound calcium and rigor S1) relative to the inhibited conformation (no bound calcium or rigor S1). In contrast, only 2-3-fold regulation is due to a change in actin affinity such as would be expected by "steric blocking" of the myosin binding site of the thin filament by tropomyosin. The binding of one ligand (either calcium or rigor-S1) produces partial activation of the rate of product dissociation, but the binding of both is required to maximally accelerate product dissociation to a rate similar to that obtained with F-actin in the absence of regulatory proteins. The data support an allosteric regulation model in which the binding of either calcium or rigor S1 alone to the thin filament shifts the equilibrium in favor of the active conformation, but full activation requires binding of both ligands.