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1.
Structure of (dG)n.(dC)n under superhelical stress and acid pH 总被引:7,自引:0,他引:7
V I Lyamichev S M Mirkin M D Frank-Kamenetskii 《Journal of biomolecular structure & dynamics》1987,5(2):275-282
We have recently shown that a (GA)n.(TC)n tract undergoes a sharp structural transition under superhelical stress (V.I. Lyamichev, S.M. Mirkin and M.D. Frank-Kamenetskii, J. Biomol. Struct. Dyn. 2,327 (1985]. Unlike the well studied transitions to the cruciform and to the Z form, this novel transition was strongly pH-dependent. We have found the (dG)n.(dC)n insert to undergo a pH-dependent structural transition similar to that of the (GA)n.(TC)n tract. These new data meet our earlier expectations and disagree with the data of D.E. Pulleyblank, D.B. Haniford and A.R. Morgan, Cell 42, 271 (1985). We conclude that a novel DNA structure (the H-form) is typical of homopurine-homopyrimidine mirror repeats (the H palindromes) under superhelical stress and/or acid pH. In the H-form the homopyrimidine strand forms a hairpin while half of the homopurine strand interacts with the hairpin forming a triplex, the other half of the homopurine strand being unstructured (V.I. Lyamichev, S.M. Mirkin and M.D. Frank-Kamenetskii, J. Biomol. Struct. Dyn. 2, 3, 667 (1986]. 相似文献
2.
Formation of intramolecular triplex in homopurine-homopyrimidine mirror repeats with point substitutions. 总被引:11,自引:7,他引:4 下载免费PDF全文
B P Belotserkovskii A G Veselkov S A Filippov V N Dobrynin S M Mirkin M D Frank-Kamenetskii 《Nucleic acids research》1990,18(22):6621-6624
We have used two-dimensional gel electrophoresis to study the structural transition to the triplex H form of sequences 5'-AAGGGAGAAXGGGGTATAGGGGYAAGAGGGAA-3' where X and Y are any DNA bases. The transition was observed at acid pH under superhelical stress. For X = Y = A or X = Y = G the sequences corresponded to homopurine-homopyrimidine mirror repeats (H-palindrome) which are known to adopt the H form under acid pH and superhelical stress. We have shown that the H form is actually formed for all X and Y, though in cases other than X = Y = A and X = Y = G the transition requires larger negative superhelical stress. Different substitutions require different superhelicity levels for the transition to occur. Theoretical analysis of the data obtained made it possible to estimate the energy cost of triplex formation due to all possible mismatched base triads. 相似文献
3.
We have constructed plasmids carrying d(AT)n.d(AT)n inserts of different lengths. Two-dimensional gel electrophoresis patterns show that an increase in the negative superhelicity of these DNAs brings about a structural transition within the inserts, resulting in a reduction of the superhelical stress. However, this reduction corresponds to the expected values neither for cruciform nor the Z form. Those DNA topoisomers in which the structural transition had occurred proved to be specifically recognizable by single-strand-specific endonuclease S1, with the cleavage site situated at the centre of the insert. These data, as well as kinetic studies, suggest that the cloned d(AT)n.d(AT)n sequences adopt a cruciform rather than the Z-form structure. We discuss plausible reasons of the discrepancy between the observed superhelical stress release and that expected for the transition of the insert to the cruciform state. 相似文献
4.
Hardies SC; Martin SL; Voliva CF; Hutchison CA d; Edgell MH 《Molecular biology and evolution》1986,3(2):109-125
5.
Structures of homopurine-homopyrimidine tract in superhelical DNA 总被引:35,自引:0,他引:35
V I Lyamichev S M Mirkin M D Frank-Kamenetskii 《Journal of biomolecular structure & dynamics》1986,3(4):667-669
For homopurine-homopyrimidine tracts in superhelical DNA, we propose a structure involving Watson-Crick and Hoogsteen paired triple helixes, hairpin loops and unstructured domains. Topologically, the whole structure is equivalent to an open region. The proposed structure is consistent with available S1 cleavage, pH and alkylation data and energetics under superhelical stress; this new structure is a much more probable candidate than the one proposed by us recently (V.I. Lyamichev, S.M. Mirkin & M.D. Frank-Kamenetskii, J. Biomole. Str. Dyns 3, 327-338, 1985). 相似文献
6.
V F Mashanski? Iu V Markov V Kh Shpunt S E Li A S Mirkin 《Arkhiv anatomii, gistologii i émbriologii》1983,84(3):53-60
Localization and distribution of the gap junctions in the human epidermis have been studied. They are mainly concentrated in the area of biologically active (acupunctive) points and in so called meridians connecting these points. A supposition is made that the gap junction system performs certain integration of the information from the skin surface and its aneural transmission to remote areas. Discovery of a regulated gap junction system in relatively low organized animals (previously described by the authors), as well as revealing of such a system in mammals, makes it possible to suppose that the system is phylogenetically the most ancient one performing a directed transmission of an information simultaneously with and besides the neural system. 相似文献
7.
A major difference between the divergence patterns within the lines-1 families in mice and voles 总被引:3,自引:0,他引:3
Vanlerberghe F; Bonhomme F; Hutchison CA d; Edgell MH 《Molecular biology and evolution》1993,10(4):719-731
L1 retroposons are represented in mice by subfamilies of interspersed
sequences of varied abundance. Previous analyses have indicated that
subfamilies are generated by duplicative transposition of a small number of
members of the L1 family, the progeny of which then become a major
component of the murine L1 population, and are not due to any active
processes generating homology within preexisting groups of elements in a
particular species. In mice, more than a third of the L1 elements belong to
a clade that became active approximately 5 Mya and whose elements are >
or = 95% identical. We have collected sequence information from 13 L1
elements isolated from two species of voles (Rodentia: Microtinae: Microtus
and Arvicola) and have found that divergence within the vole L1 population
is quite different from that in mice, in that there is no abundant
subfamily of homologous elements. Individual L1 elements from voles are
very divergent from one another and belong to a clade that began a period
of elevated duplicative transposition approximately 13 Mya. Sequence
analyses of portions of these divergent L1 elements (approximately 250 bp
each) gave no evidence for concerted evolution having acted on the vole L1
elements since the split of the two vole lineages approximately 3.5 Mya;
that is, the observed interspecific divergence (6.7%-24.7%) is not larger
than the intraspecific divergence (7.9%-27.2%), and phylogenetic analyses
showed no clustering into Arvicola and Microtus clades.
相似文献
8.
Molecular phylogeny and divergence times of drosophilid species 总被引:32,自引:15,他引:17
The phylogenetic relationships and divergence times of 39 drosophilid
species were studied by using the coding region of the Adh gene. Four
genera--Scaptodrosophila, Zaprionus, Drosophila, and Scaptomyza (from
Hawaii)--and three Drosophila subgenera--Drosophila, Engiscaptomyza, and
Sophophora--were included. After conducting statistical analyses of the
nucleotide sequences of the Adh, Adhr (Adh-related gene), and nuclear rRNA
genes and a 905-bp segment of mitochondrial DNA, we used Scaptodrosophila
as the outgroup. The phylogenetic tree obtained showed that the first major
division of drosophilid species occurs between subgenus Sophophora (genus
Drosophila) and the group including subgenera Drosophila and Engiscaptomyza
plus the genera Zaprionus and Scaptomyza. Subgenus Sophophora is then
divided into D. willistoni and the clade of D. obscura and D. melanogaster
species groups. In the other major drosophilid group, Zaprionus first
separates from the other species, and then D. immigrans leaves the
remaining group of species. This remaining group then splits into the D.
repleta group and the Hawaiian drosophilid cluster (Hawaiian Drosophila,
Engiscaptomyza, and Scaptomyza). Engiscaptomyza and Scaptomyza are tightly
clustered. Each of the D. repleta, D. obscura, and D. melanogaster groups
is monophyletic. The splitting of subgenera Drosophila and Sophophora
apparently occurred about 40 Mya, whereas the D. repleta group and the
Hawaiian drosophilid cluster separated about 32 Mya. By contrast, the
splitting of Engiscaptomyza and Scaptomyza occurred only about 11 Mya,
suggesting that Scaptomyza experienced a rapid morphological evolution. The
D. obscura and D. melanogaster groups apparently diverged about 25 Mya.
Many of the D. repleta group species studied here have two functional Adh
genes (Adh-1 and Adh-2), and these duplicated genes can be explained by two
duplication events.
相似文献
9.
Mirkin S. M. Zaitsev E. N. Panyutin I. G. Lyamichev V. I. 《Molecular genetics and genomics : MGG》1984,194(3):508-512
Molecular Genetics and Genomics - This study deals with the effects of a temperature-sensitive (ts) mutation at the gene encoding the DNA gyrase B subunit (gyrB ts) and a deletion of the top gene... 相似文献
10.
William Schumacher Ph.D. Bernard L. Mirkin J. R. Sheppard 《Molecular and cellular biochemistry》1984,59(1-2):173-181
Summary The -adrenergic receptor, transduction processes and catalytic activity of the adenylate cyclase enzyme complex have been investigated in rabbit heart at different stages of biological maturation. The binding of [3H]-dihydroalprenolol to a washed membrane preparation isolated from rabbit ventricular muscle was used to characterize -adrenergic receptors. Significant age-related differences were noted in -receptor affinity (Kd) and density (RD) of neonatal and adult animals; the adult Kd was 3.7-fold greater and the RD 2-fold higher than the neonates. No significant differences in these parameters were detected among the 27-day old fetus and the 1- and 7-day old neonates. Age-dependent differences in agonist isoproterenol affinity for the receptor were not observed in contrast to the significant changes in antagonist (DHA) affinity.Age-related changes in receptor affinity were also quantitated by determining the inhibitory potency of alprenolol on isoproterenol stimulated adenylate cyclase enzyme activity. A decreased affinity of the -adrenergic receptor for alprenolol in the adult heart was indicated by a 3.7-fold greater Ki for the adult than the 1-day old neonate. Ontogenic variations in the coupling efficiency between the receptor and catalytic components of the adenylate cyclase complex were also evaluated. The Kd of the -adrenergic receptor for isoproterenol and the EC50 for adenylate cyclase stimulation were determined under similar conditions. The corresponding coupling index (Kd/EC50) was found to be 2.4-fold greater in the 1-day old neonate than adult, suggesting that for a given percentage increase in adenylate cyclase activity, a lower percentage of -adrenergic receptor sites need be occupied in the neonate. These data extend previous studies (29) and indicate all components of the rabbit heart adenylate cyclase enzyme complex (i.e., the -adrenergic receptor, the GTP-dependent transduction event, and the catalytic subunit) exhibit significant developmental changes. 相似文献