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111.
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.
相似文献
112.
T. Aerts J. Clauwaert P. Haezebrouck E. Peeters H. Van Dael 《European biophysics journal : EBJ》1997,25(5-6):445-454
We have studied the quaternary structure of α-crystallin in the presence of increasing concentrations of amphiphilic and neutral detergents using gel filtration, light-scattering,
boundary and equilibrium sedimentation. We observed a continuous reduction of the molar mass of the polymeric α-crystallin on increasing the concentration of sodium dodecyl sulphate from 0.1 mM to 5 mM, ending up with the monomeric peptides.
Dodecyltrimethylammonium bromide also disrupts the oligomeric structure of α-crystallin but the interaction appears to be cooperative: in the sharp transition region (for a 1 mg/ml protein solution)
from 3 to 8 mM of the detergent, only the native protein and a mixture of monomeric and dimeric peptide-DTAB complexes can
be observed. Concomitant studies of the circular dichroism in the far UV revealed a substantial decrease of the β-sheet and increase of the α-helix secondary structure. The latter can be related to the presence of amphiphilic polypeptide sequences in the constituent
αA and αB peptides. These studies reveal for the first time a direct relation between changes in the secondary structure of the αA and αB peptides and the formation of the oligomeric α-crystallin structure: the binding of the amphiphilic detergent reduces the β-sheet content, induces the formation of α-helix secondary structure and reduces the tendency of the peptide to form large aggregates. The different mechanisms for
reducing the oligomeric size by anionic and cationic detergents with identical apolar parts stresses the importance of charge
interactions. Our findings support some aspects of the micelle model of α-crystallin and can be related to its chaperone activity.
Accepted: 18 October 1996 相似文献
113.
A flux analysis of glucose metabolism in the filamentous fungus Rhizopus oryzae was achieved using a specific radioactivity curve-matching program, TFLUX. Glycolytic and tricarboxylic acid cycle intermediates labeled through the addition of extracellular [U-14C]glucose were isolated and purified for specific radioactivity determinations. This information, together with pool sizes and the rates of glucose utilization and end product production, provided input for flux maps of the metabolic network under two different experimental conditions. Based upon the flux analysis of this system, a mutant of R. oryzae with higher lactate and lower ethanol yields than the parent was sought for and found. 相似文献
114.
Studies of cryptogam responses to climate change in the polar regions are scarce because these slow-growing organisms require long-term monitoring studies. Here, we analyse the response of a lichen and moss community to 10 years of passive environmental manipulation using open-top chambers (OTCs) in the maritime Antarctic region. Cover of the dominant lichen Usnea antarctica declined by 71 % in the OTCs. However, less dominant lichen species showed no significant responses except for an increase in Ochrolechia frigida, which typically covered dying lichen and moss vegetation. There were no detectable responses in the moss or associated micro-arthropod communities to the influence of the OTCs. Based on calculated respiration rates, we hypothesise that the decline of U. antarctica was most likely caused by increased net winter respiration rates (11 %), driven by the higher temperatures and lower light levels experienced inside the OTCs as a result of greater snow accumulation. During summer, U. antarctica appears unable to compensate for this increased carbon loss, leading to a negative carbon balance on an annual basis, and the lichen therefore appears to be vulnerable to such climate change simulations. These findings indicate that U. antarctica dominated fell-fields may change dramatically if current environmental change trends continue in the maritime Antarctic, especially if associated with increases in winter snow depth or duration. 相似文献
115.
116.
117.
Head kinematics during aquatic feeding of the Australian long-necked turtle (Chelodina) were studied by means of high speed video recordings. Buccal expansion was assessed by calculation of elliptical cross-sectional surfaces. Further, displacements of head, carapace, and prey in the earth bound frame, of the prey relative to the center of the gape, and of the head relative to the carapace were determined. Rates of change (velocities) of all these variables were calculated. These data are combined with information on the osteology and myology of the head. The robust development of the large hyobranchial apparatus, the massive intercornuatus muscle, and the presence of the branchiosquamosus muscle were related to aquatic feeding skills. Head kinematics are variable in amplitude and relative timing, but proceed always in a rostrocaudal sequence. According to their effect on the prey, two components are distinguished in the process of expansion. The first compensates for head/body movements (compensatory suction). The second causes distinct acceleration of water and prey (inertial suction). The latter component is mainly driven by the abduction of the second branchial arch. In spite of largely different structural solutions, optimal feeding conditions as deduced for suction in feeding fishes are also employed by Chelodina. This further promotes the assumption that hydrodynamics constrain evolutive solutions for aquatic feeding. J. Morphol. 233:113–125, 1997. © 1997 Wiley-Liss, Inc. 相似文献
118.
Plant species traits are the predominant control on litter decomposition rates within biomes worldwide 总被引:9,自引:0,他引:9
Cornwell WK Cornelissen JH Amatangelo K Dorrepaal E Eviner VT Godoy O Hobbie SE Hoorens B Kurokawa H Pérez-Harguindeguy N Quested HM Santiago LS Wardle DA Wright IJ Aerts R Allison SD van Bodegom P Brovkin V Chatain A Callaghan TV Díaz S Garnier E Gurvich DE Kazakou E Klein JA Read J Reich PB Soudzilovskaia NA Vaieretti MV Westoby M 《Ecology letters》2008,11(10):1065-1071
Worldwide decomposition rates depend both on climate and the legacy of plant functional traits as litter quality. To quantify the degree to which functional differentiation among species affects their litter decomposition rates, we brought together leaf trait and litter mass loss data for 818 species from 66 decomposition experiments on six continents. We show that: (i) the magnitude of species-driven differences is much larger than previously thought and greater than climate-driven variation; (ii) the decomposability of a species' litter is consistently correlated with that species' ecological strategy within different ecosystems globally, representing a new connection between whole plant carbon strategy and biogeochemical cycling. This connection between plant strategies and decomposability is crucial for both understanding vegetation-soil feedbacks, and for improving forecasts of the global carbon cycle. 相似文献
119.
Omar JM Hamza Mecky IN Matee Mainen J Moshi Elison NM Simon Ferdinand Mugusi Frans HM Mikx Wim H van Palenstein Helderman Antonius JMM Rijs André JAM van der Ven Paul E Verweij 《BMC microbiology》2008,8(1):135
Background
In Tanzania, little is known on the species distribution and antifungal susceptibility profiles of yeast isolates from HIV-infected patients with primary and recurrent oropharyngeal candidiasis. 相似文献120.
Herrel A Schaerlaeken V Ross C Meyers J Nishikawa K Abdala V Manzano A Aerts P 《Integrative and comparative biology》2008,48(2):261-271
Electromyography (EMG), or the study of muscle activation patterns,has long been used to infer central nervous system (CNS) controlof the musculoskeletal system and the evolution of that control.As the activation of the muscles at the level of the peripheryis a reflection of the interaction of descending influencesand local reflex control, EMG is an important tool in integratedinvestigations of the evolution of coordination in complex,musculoskeletal systems. Yet, the use of EMG as a tool to understandthe evolution of motor control has its limitations. We herereview the potential limitations and opportunities of the useof EMG in studying the evolution of motor control in vertebratesand provide original previously unpublished data to illustratethis. The relative timing of activation of a set of musclescan be used to evaluate CNS coordination of the components ina musculoskeletal system. Studies of relative timing revealtask-dependent variability in the recruitment of different populationsof muscle fibers (i.e., different fiber types) within a singlemuscle, and left–right asymmetries in activation thatneed to be taken into account in comparative studies. The magnitudeof muscle recruitment is strongly influenced by the instantaneousdemands imposed on the system, and is likely determined by localreflex-control systems. Consequently, using EMG to make meaningfulinferences about evolutionary changes in musculoskeletal controlrequires comparisons across similar functional tasks. Moreover,our data show that inferences about the evolution of motor controlare limited in their explanatory power without proper insightsinto the kinematics and dynamics of a system. 相似文献