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1.
The alpha-like globin gene cluster in rabbits contains embryonic zeta-
globin genes, an adult alpha-globin gene, and theta-globin genes of
undetermined function. The basic arrangement of genes, deduced from
analysis of cloned DNA fragments, is 5'-zeta 0-zeta 1-alpha 1-theta 1- zeta
2-zeta 3-theta 2-3'. However, the pattern of restriction fragments
containing zeta- and theta-globin genes varies among individual rabbits.
Analysis of BamHI fragments of genomic DNA from 24 New Zealand white
rabbits revealed eight different patterns of fragments containing
zeta-globin genes. The large BamHI fragments containing genes zeta 0 and
zeta 1 are polymorphic in length, whereas a 1.9-kb fragment containing the
zeta 2 gene and the 3.5-kb fragment containing the zeta 3 gene do not vary
in size. In contrast to this constancy in the size of the restriction
fragments, the copy number of the zeta 2 and zeta 3 genes does vary among
different rabbits. No length polymorphism was detected in the BamHI
fragments containing the theta-globin genes, but again the copy number
varies for restriction fragments containing the theta 2 gene. The alpha 1-
and theta 1-globin genes are located in a nonpolymorphic 7.2-kb BamHI
fragment. The combined data from hybridization with both zeta and theta
probes shows that the BamHI cleavage pattern does not vary within the
region 5'-alpha 1-theta 1- zeta 2-zeta 3-theta 2-3', but the pattern
genomic blot-hybridization patterns for the progeny of parental rabbits
with different zeta-globin gene patterns shows that the polymorphic
patterns are inherited in a Mendelian fashion. Two different haplotypes
have been mapped based on the genomic blot-hybridization data. The
variation in the alpha-like globin gene cluster in the rabbit population
results both from differences in the copy number of the duplication block
containing the zeta-zeta-theta gene set and from the presence or absence of
polymorphic BamHI sites.
相似文献
2.
Trimethyloxonium modification of single batrachotoxin-activated sodium channels in planar bilayers. Changes in unit conductance and in block by saxitoxin and calcium 总被引:13,自引:9,他引:4 下载免费PDF全文
Single batrachotoxin-activated sodium channels from rat brain were modified by trimethyloxonium (TMO) after incorporation in planar lipid bilayers. TMO modification eliminated saxitoxin (STX) sensitivity, reduced the single channel conductance by 37%, and reduced calcium block of inward sodium currents. These effects always occurred concomitantly, in an all-or-none fashion. Calcium and STX protected sodium channels from TMO modification with potencies similar to their affinities for block. Calcium inhibited STX binding to rat brain membrane vesicles and relieved toxin block of channels in bilayers, apparently by competing with STX for the toxin binding site. These results suggest that toxins, permeant cations, and blocking cations can interact with a common site on the sodium channel near the extracellular surface. It is likely that permeant cations transiently bind to this superficial site, as the first of several steps in passing inward through the channel. 相似文献
3.
M Proulx L Duplain L Lacoste M Yaguchi J Lapointe 《The Journal of biological chemistry》1983,258(2):753-759
The glutamyl-tRNA synthetase from Bacillus subtilis has been purified to homogeneity. It is a monomer of Mr = 65,500 whose NH2-terminal sequence is Met-Asn-Glu-Val-Arg-Val-Arg-Tyr-Ser-Pro-Ser-Pro-Thr-Gly-His-Leu. The number of tryptic peptides indicates the absence of a significant amount of sequence duplication. Under certain conditions, this monomeric enzyme is co-purified with a polypeptide beta of Mr = 46,000, which increases the affinity of the enzyme about 10-fold for glutamate and for ATP, and stabilizes it against heat inactivation. gamma-Globulins prepared against the monomeric enzyme can inhibit completely the glutamyl-tRNA synthetase activity of a B. subtilis extract and precipitate from this extract both the monomeric enzyme and the regulatory factor beta. These anti-alpha immunoglobulins do nt precipitate pure beta. These results show that the glutamyl-tRNA synthetase of B. subtilis has a structure similar to that of the Escherichia coli enzyme (Lapointe, J., and S?ll, D. (1972) J. Biol. Chem. 247, 4966-4974) and indicate that the beta factor has a function in the regulation of glutamyl-tRNA biosynthesis in vivo. 相似文献
4.
Purification of proteins similar to HPr and enzyme I from the oral bacterium Streptococcus salivarius. Biochemical and immunochemical properties 总被引:13,自引:0,他引:13
The phosphoenolpyruvate:sugar phosphotransferase system (PTS) is made of several proteins. Two of them are designated general proteins because they are required for the transport and phosphorylation of all sugars of the PTS. These two proteins are found in the soluble fraction of cellular extracts and are termed HPr and enzyme I (EI). We reported in this work the purification and the characterization of these two proteins from Streptococcus salivarius ATCC 25975. HPr was purified by DEAE-cellulose chromatography, molecular sieving on Ultrogel AcA44, and carboxymethylcellulose chromatography. Sodium dodecyl sulfate electrophoresis in the presence of urea revealed a single band with a molecular weight of 6700. The protein contained no tryptophan and had a pI of 4.8. The purification scheme of EI was as follows: DEAE-cellulose chromatography, hydroxylapatite chromatography, DEAE-Sephadex A-50 chromatography, preparative electrophoresis, and molecular sieving on Ultrogel AcA34. The five-step purification for EI produced a 199-fold purified preparation with a specific activity of 530 mumol of HPr phosphorylated per minute per milligram of protein at 37 degrees C. The fraction obtained after filtration on Ultrogel AcA34 gave one band (68 000) on sodium dodecyl sulfate - polyacrylamide gel electrophoresis. The molecular weight of the native enzyme determined by gel filtration at 4 degrees C was 135 000, suggesting that it was a dimer. Enzyme I had a pI of 4.2, a pH optimum of 6.7, a Km for HPr of about 27 microM, a Km for phosphoenolpyruvate of 0.48 mM, and kinetics that were consistent with a Ping-Pong mechanism. Evidence had been obtained which indicated that S. salivarius enzyme I was antigenically very similar to enzyme I from various strains of Streptococcus mutans, but not to the enzyme from Bacillus subtilis, Staphylococcus aureus, Streptococcus faecalis, and Escherichia coli. 相似文献
5.
Lysis of erythrocytes by long-chain acyl esters of carnitine 总被引:1,自引:0,他引:1
6.
An enzyme with phospholipase Al activity was purified some 500-fold from Escherichia coli cell homogenates. Lipase, phospholipase A2, and lysophospholipase copurified with phospholipase A1 and the four activities displayed similar susceptibility to heat treatment. The phospholipase A and lipase activities were recovered in a single band when partially purified preparations were subjected to SDS gel electrophoresis. Phospholipase, lysophospholipase, and lipase all required Ca2+ for activity. Phosphatidylcholine, phosphatidylethanolamine, and their lyso analogues were all hydrolysed at equivalent rates and these were substantially greater than the rate of methylpalmitate or tripalmitoylglycerol hydrolyses under similar incubation conditions. Evidence for a direct but slow hydrolysis of the ester at position 2 of phosphoglyceride was obtained; however, release of fatty acid from this position is mostly indirect involving acyl migration to position 1 and subsequent release of the translocated fatty acid. Escherichia coli, therefore, appears to possess a lipolytic enzyme of broad substrate specificity acting mainly at position 1 but also at position 2 of phosphoglycerides and on triacylglycerols and methyl fatty-acid esters. 相似文献
7.
Abstract Opportunistic sightings and strandings of Caperea marginata (n=196) from the vicinity of Australia and New Zealand (1884 to early 2007) were used to relate geographic and temporal patterns to oceanographic and broad-scale climatic variability. Records were not uniformly distributed along the coast and more (69%) were from Australia than New Zealand. Seven coastal whale ‘hotspots’ were identified which accounted for 61% of records with locality data. Half of the hotspot records were from southeast (37) and northwest (20) Tasmania—others each had 9–15 events. Upwelling and/or high zooplankton abundance has been documented near all whale hotspots. Records of C. marginata occurred in all months, with 75% in spring and summer. Inter-annual variability showed broad agreement between increased whale records (usually in spring/summer) and strongly positive ‘Niño 3.4’ during 1980–1995 but not thereafter. Coastal upwelling and productivity increase during climatic phenomena such as El Niño and are likely to be quickly beneficial to plankton-feeding whales such as C. marginata. 相似文献
8.
9.
Enumerating phytoplankton with an upright compound microscope using a modified settling chamber 总被引:1,自引:0,他引:1
A modified settling chamber is described which permits the use of an upright compound microscope for phytoplankton enumerations. The chamber is composed of a 75 × 51 mm rectangular or 70 mm round-glass microslide base with a 130 m thick piece of sheet styrene attached to the upper surface. A circular cell is cut into the styrene material making a 26 mm diameter chamber which is approximately 130–150 m deep. Settling procedures follow Utermöhl's technique, with the use of a 0.13–0.15 mm thick coverslip (50 × 45 mm) to cover the chamber. The overall thickness of the settling slide is 1.13 mm which does not impact on the optical requirements for most objectives, including oil immersion objectives. The chamber encloses a total volume of 69–80 mm3. No statistical differences are observed in cell, filament or colony counts between the new and traditional chambers. Furthermore, count comparisons at different cell concentrations using the new chambers give consistent results. Thus, the resolution and availability of an upright microscope makes the use of the new settling chamber an attractive method for phytoplankton counting, especially in teaching situations. 相似文献
10.
Older males signal more reliably 总被引:4,自引:0,他引:4
Proulx SR Day T Rowe L 《Proceedings. Biological sciences / The Royal Society》2002,269(1507):2291-2299
The hypothesis that females prefer older males because they have higher mean fitness than younger males has been the centre of recent controversy. These discussions have focused on the success of a female who prefers males of a particular age class when age cues, but not quality cues, are available. Thus, if the distribution of male quality changes with age, such that older males have on average genotypes with higher fitness than younger males, then a female who mates with older males has fitter offspring, which allows the female preference to spread through a genetic correlation. We develop a general model for male display in a species with multiple reproductive bouts that allows us to identify the conditions that promote reliable signalling within an age class. Because males have opportunities for future reproduction, they will reduce their levels of advertising compared with a semelparous species. In addition, because higher-quality males have more future reproduction, they will reduce their advertising more than low-quality males. Thus, the conditions for reliable signalling in a semelparous organism are generally not sufficient to produce reliable signalling in species with multiple reproductive bouts. This result is due to the possibility of future reproduction so that, as individuals age and the opportunities for future reproduction fade, signalling becomes more reliable. This provides a novel rationale for female preference for older mates; older males reveal more information in their sexual displays. 相似文献