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1.
E. Rosato A. A. Peixoto A. Gallippi C. P. Kyriacou R. Costa 《Journal of molecular evolution》1996,42(4):392-408
The D. melanogaster clock gene period (per) is an internally repetitive gene encoding a tandem array of Thr-Gly codons that are highly polymorphic in length in European
natural populations. The two major length variants, (Thr-Gly)20 and (Thr-Gly)17, show a highly significant latitudinal cline. In this study we present the complete sequence of the Thr-Gly region of 91
individuals from 6 natural populations of D. melanogaster, 5 from Europe and 1 from North Africa. We further characterized these 91 individuals for polymorphic sites in two other regions,
one upstream and one downstream of the Thr-Gly repeat. We used the haplotypic combinations of Thr-Gly allele with flanking
markers in an attempt to identify the mechanisms involved in the evolution of the D. melanogaster Thr-Gly region and to infer the phylogenetic relationship existing among the Thr-Gly alleles. We observe evidence for both
intra- and interallelic mutational mechanisms, including replication slippage, unequal crossing-over, and gene conversion.
Received: 22 August 1995 / Accepted: 17 October 1995 相似文献
2.
The Drosophila fat body protein 2 gene (Fbp2) is an ancient duplication of the alcohol dehydrogenase gene (Adh) which encodes a protein that differs substantially from ADH in its methionine content. In D. melanogaster, there is one methionine in ADH, while there are 51 (20% of all amino acids) in FBP2. Methionine is involved in 46% of amino
acid replacements when Fbp2 DNA sequences are compared between D. melanogaster and D. pseudoobscura. Methionine accumulation does not affect conserved residues of the ADH-ADHr-FBP2 multigene family. The multigene family has evolved by replacement of mildly hydrophobic amino acids by methionine with
no apparent reversion. Its short-term evolution was compared between two Drosophila species, while its long-term evolution was compared between two genera belonging respectively to acalyptrate and calyptrate
Diptera, Drosophila and Sarcophaga. The pattern of nucleotide substitution was consistent with an independent accumulation of methionines at the Fbp2 locus in each lineage. Under a steady-state model, the rate of methionine accumulation was constant in the lineage leading
to Drosophila, and was twice as fast as that in the calyptrate lineage. Substitution rates were consistent with a slight positive selective
advantage for each methionine change in about one-half of amino acid sites in Drosophila. This shows that selection can potentially account for a large proportion of amino acid replacements in the molecular evolution
of proteins.
Received: 12 December 1994 / Accepted: 15 April 1996 相似文献
3.
Shuji Shigenobu Hidemi Watanabe Yoshiyuki Sakaki Hajime Ishikawa 《Journal of molecular evolution》2001,53(4-5):377-386
Endosymbiotic bacteria live in animal cells and are transmitted vertically at the time of the host's reproduction. In view
of their small and asexual populations with infrequent chances of recombination, these endocellular bacteria are expected
to accumulate mildly deleterious mutations. Previous studies showed that the DNA sequences of these bacteria evolved faster
than those of free-living bacteria. In this study, we compared all the ORFs of Buchnera, an endocellular bacterial symbiont of aphids, with those of 34 other prokaryotic organisms and estimated the effect of the
accelerated evolution of Buchnera on the functions of its proteins. It was revealed that Buchnera proteins contain many mutations at the sites where sequences are conserved in their orthologues in many other organisms.
In addition, amino acid replacements at the conserved sites are mostly changes to physicochemically different amino acids.
These results suggest that functions and conformations of Buchnera proteins have been seriously impaired or strongly modified. Indeed, extensive loss of functional motifs was observed in some
Buchnera proteins. In many Buchnera proteins mutations were not detected evenly throughout each molecule but tended to accumulate in some functional units, possibly
leading to loss of specific functions. As Buchnera has an unusual and limited gene repertory, it is conceivable that the manner of interactions among its proteins has been
changed, and thus, functional constraints over their amino acid residues have also been changed during evolution. This may
account for the loss of some functional units only in the Buchnera proteins. We obtained evidence that amino acid replacements in Buchnera were not always deleterious, but neutral or, in some cases, even positively selected.
Received: 14 December 2000 / Accepted: 12 March 2001 相似文献
4.
The polymeric ubiquitin (poly-u) genes are composed of tandem 228-bp repeats with no spacer sequences between individual
monomer units. Ubiquitin is one of the most conserved proteins known to date, and the individual units within a number of
poly-u genes are significantly more similar to each other than would be expected if each unit evolved independently. It has
been proposed that the rather striking similarity among poly-u monomers in some lineages is caused by a series of homogenization
events. Here we report the sequences of the polyubiquitin-C (Ubc) genes in two mouse strains. Analysis of these sequences,
as well as those of the previously reported Chinese hamster and rat poly-u genes, supports the assertion that the homogenization
of the ubiquitin-C gene in rodents is due to unequal crossing-over events. The sequence divergence of noncoding DNA was used
to estimate the frequency of unequal crossing-over events (6.3 × 10−5 events per generation) in the Ubc gene, as well as to provide evidence of apparent selection in the poly-u gene. 相似文献
5.
Jean-Luc Desseyn Marie-Pierre Buisine Nicole Porchet Jean-Pierre Aubert Pierre Degand Anne Laine 《Journal of molecular evolution》1998,46(1):102-106
The four human mucin genes MUC6, MUC2, MUC5AC, and MUC5B are located at chromosome 11p15.5. It has been demonstrated that the three mucins MUC2, MUC5AC, and MUC5B contain several
Cys-subdomains of 108 amino acid residues. In contrast, little information is available concerning MUC6. These Cys-subdomains
contain 10 cysteine residues that have a highly conserved position. We present here a coherent probable evolutionary history
of this human gene family after comparison of the nucleotide sequences of these Cys-subdomains. The three MUC loci MUC2, MUC5AC, and MUC5B may have evolved from a common ancestral gene by two successive duplications. Moreover, we can postulate that MUC5AC and MUC5B have evolved in a concerted manner, while MUC2 has evolved separately.
Received: 30 January 1997 / Accepted: 17 April 1997 相似文献
6.
Jan Kwiatowski Michal Krawczyk Michal Jaworski Douglas Skarecky F.J. Ayala 《Journal of molecular evolution》1997,44(1):9-22
We have studied the evolution of Gpdh in 18 fruitfly species by sequencing 1,077 nucleotides per species on average. The region sequenced includes four exons coding
for 277 amino acids and three variable-length introns. Phylogenies derived by a variety of methods confirm that the nominal
genus Zaprionus belongs within the genus Drosophila, whereas Scaptodrosophila and Chymomyza are outside. The rate of GPDH evolution is erratic. The rate of amino acid replacements in a lineage appears to be 1.0 ×
10−10/site/year when Drosophila species are considered (diverged up to 55 million years ago), but becomes 2.3 × 10−10 when they are compared to Chymomyza species (divergence around 60 My ago), and 4.6 × 10−10 when species of those two genera are compared with the medfly Ceratitis capitata (divergence around 100 My ago). In order to account for these observations, the rate of amino acid replacement must have
been 15 or more times greater in some lineages and at some times than in others. At the nucleotide level, however, Gpdh evolves in a fairly clockwise fashion.
Received: 13 June 1996 / Accepted: 16 August 1996 相似文献
7.
The idea that the pattern of point mutation in Drosophila has remained constant during the evolution of the genus has recently been challenged. A study of the nucleotide composition
focused on the Drosophila
saltans group has evidenced unsuspected nucleotide composition differences among lineages. Compositional differences are associated
with an accelerated rate of amino acid replacement in functionally less constrained regions. Here we reassess this issue from
a different perspective. Adopting a maximum-likelihood estimation approach, we focus on the different predictions that mutation
and selection make about the nonsynonymous-to-synonymous rate ratio. We investigate two gene regions, alcohol dehydrogenase
(Adh) and xanthine dehydrogenase (Xdh), using a balanced data set that comprises representatives from the melangaster, obscura, saltans, and willistoni groups. We also consider representatives of the Hawaiian picture-winged group. These Hawaiian species are known to have experienced
repeated bottlenecks and are included as a reference for comparison. Our results confirm patterns previously detected. The
branch ancestral to the fast-evolving willistoni/saltans lineage, where most of the change in GC content has occurred, exhibits an excess of synonymous substitutions. The shift in
mutation bias has affected the extent of the rate variation among sites in Xdh.
Received: 4 May 1999 / Accepted: 26 July 1999 相似文献
8.
Charles M. Matthews Cassandra J. Vandenberg Clive N.A. Trotman 《Journal of molecular evolution》1998,46(6):729-733
The Artemia hemoglobin is a dimer comprising two nine-domain covalent polymers in quaternary association. Each polymer is encoded by
a gene representing nine successive globin domains which have different sequences and are presumed to have been copied originally
from a single-domain gene. Two different polymers exist as the result of a complete duplication of the nine-domain gene, allowing
the formation of either homodimers or the heterodimer. The total population size of 18 domains comprising nine corresponding
pairs, coupled with the probability that they reflect several hundred million years of evolution in the same lineage, provides
a unique model in which the process of gene multiplication can be analyzed. The outcome has important implications for the
reliability of local molecular clocks.
The two polymers differ from each other at 11.7% of amino acid sites; however when corresponding individual domains are compared
between polymers, amino acid substitution fluctuates by a factor of 2.7-fold from lowest to highest. This variation is not
obvious at the DNA level: Domain pair identity values fluctuate by 1.3-fold. Identity values are, however, uncorrected for
multiple substitutions, and both silent and nonsilent changes are pooled. Therefore, to determine the variability in relative
substitution rates at the DNA level, we have used the method of Li (1993, J Mol Evol 36:96–99) to determine estimates of nonsynonymous (K
A
) and synonymous (K
S
) substitutions per site for the nine pairs of domains. As expected, the overall level of silent substitutions (K
S
of 56.9%) far exceeded nonsilent substitutions (K
A
of 6.7%); however, for corresponding domain pairs, K
A
fluctuates by 2.3-fold and K
S
by 1.7-fold. The large discrepancies reflected in the expressed protein have accrued within a single lineage and the implication
is that divergence dates of different genera based on amino acid sequences, even with well-studied proteins of reasonable
size, can be wrong by a factor well in excess of 2.
Received: 4 June 1997 / Accepted: 17 December 1997 相似文献
9.
Multiple phospholipase A2 (PLA2) isoenzymes found in a single snake venom induce a variety of pharmacological effects. These multiple forms are formed by
gene duplication and accelerated evolution of exons. We examined the amino acid sequences of 127 snake venom PLA2 enzymes and their homologues to study in which location most natural substitutions occur. Our data show that hot spots of
amino acid substitutions in this group of proteins occur mostly on the surface. A logistic model correlating the substitution
rates of each amino acid residue with their surface accessibility indicates that the probability of natural substitutions
occurring in the fully exposed residue is 2.6–3.5 times greater than that of substitutions occurring in buried residues. These
surface substitutions play a significant role in the evolution of new PLA2 isoenzymes by altering the specificity of targeting to various tissues or cells, resulting in distinct pharmacological effects.
Thus natural substitutions in PLA2 enzymes, in contrast to popular belief, are not random substitutions but appear to be directed toward modifying the molecular
surface.
Received: 11 May 1998 / Accepted: 29 June 1998 相似文献
10.
Chromosome terminal, complex repeats in the dipteran Chironomus pallidivittatus show rapid concerted evolution during which there is remarkably efficient homogenization of the repeat units within and between
chromosome ends. It has been shown previously that gene conversion is likely to be an important component during these changes.
The sequence evolution could be a result of different processes—exchanges between repeats in the tandem array as well as information
transfer between units in different chromosomes—and is therefore difficult to analyze in detail. In this study the concerted
evolution of a region present only once per chromosome, at the junction between the telomeric complex repeats and the subtelomeric
DNA was therefore investigated in the two sibling species C. pallidivittatus and C. tentans. Material from individual microdissected chromosome ends was used, as well as clones from bulk genomic DNA. On the telomeric
side of the border pronounced species-specific sequence differences were observed, the patterns being similar for clones of
different origin within each species. Mutations had been transmitted efficiently between chromosomes also when adjoining,
more distally localized DNA showed great differences in sequence, suggesting that gene conversion had taken place. The evolving
telomeric region bordered proximally to subtelomeric DNA with high evolutionary constancy. More proximally localized, subtelomeric
DNA evolved more rapidly and showed heterogeneity between species and chromosomes.
Received: 24 September 1997 / Accepted: 24 November 1997 相似文献
11.
In eight hagfish species, it is known that chromosome elimination occurs during early embryogenesis, and some highly repetitive
DNA families, restricted to germ cells, have been isolated. One of these families, ``EEEo2,' has been isolated as DNA fragments
by restriction enzyme analyses from Eptatretus okinoseanus and E. cirrhatus. In this study, EEEo2 sequences were isolated from germline DNA in E. burgeri, Paramyxine sheni, and P. atami using PCR methods. Sequence analysis revealed that these sequences are intraspecifically homogeneous, except in E. burgeri, and are interspecifically conserved with heterogeneity. The intraspecific sequence variability tends to decrease as the copy
number increases. These results indicate that EEEo2 has evolved in a concerted manner. Moreover, an ancestral repeating motif
consisting of triplicate subrepeats was deduced. These results suggest that EEEo2 arose as an initial amplification of this
subrepeat and has evolved by saltatory replication. Phylogenetic analyses suggested the possibility that EEEo2 in E. okinoseanus and E. cirrhatus has been subjected to strong homogenizing forces for concerted evolution, whereas the force is weak in E. burgeri. In addition, EEEo2 in P. sheni and P. atami appear to have been incompletely subjected to these forces. Chromosomal in situ hybridization experiments revealed that EEEo2
sequences were located along almost their entire length of several heterochromatic chromosomes that are restricted to germ
cells. These chromosomes are disposed to form a secondary association during the first meiotic metaphases, except in P. sheni. This chromosomal distribution may promote a concerted mode of sequence evolution in both nonhomologous chromosomes and homologous
chromosomes and reflect the differential driving forces between species.
Received: 17 April 1999 / Accepted: 10 September 1999 相似文献
12.
Southern hybridization data suggest that the male sex-determining locus, Sry, is often duplicated in rodents. Here we explore DNA sequence evolution of orthologous and paralogous copies of Sry isolated from six species of African murines. PCR amplification followed by direct sequencing revealed from two to four copies
of Sry per species. All copies include a long open reading frame, with a stop codon that coincides closely with the stop codon of
the house mouse, Mus musculus, a species known to have a single copy of Sry. A phylogenetic analysis suggests that there are at least seven paralogous copies of Sry in this group of rodents. Putative orthologues are identical; sequence divergence among putative paralogues ranges from 1
to 8% (excluding the CAG repeat), with much lower levels of divergence in the high-mobility group (HMG-box) region than in
the C-terminal region. A high proportion of nucleotide substitutions in both regions result in amino-acid replacement. The
long open reading frame, conserved HMG-box, and pattern of evolution of the putative paralogues suggest that they are functional.
Received: 4 October 1996 / Accepted: 17 January 1997 相似文献
13.
14.
A Survey of the Molecular Evolutionary Dynamics of Twenty-Five Multigene Families from Four Grass Taxa 总被引:10,自引:0,他引:10
We surveyed the molecular evolutionary characteristics of 25 plant gene families, with the goal of better understanding general
processes in plant gene family evolution. The survey was based on 247 GenBank sequences representing four grass species (maize,
rice, wheat, and barley). For each gene family, orthology and paralogy relationships were uncertain. Recognizing this uncertainty,
we characterized the molecular evolution of each gene family in four ways. First, we calculated the ratio of nonsynonymous
to synonymous substitutions (d
N/d
S) both on branches of gene phylogenies and across codons. Our results indicated that the d
N/d
S ratio was statistically heterogeneous across branches in 17 of 25 (68%) gene families. The vast majority of d
N/d
S estimates were <<1.0, suggestive of selective constraint on amino acid replacements, and no estimates were >1.0, either across
phylogenetic lineages or across codons. Second, we tested separately for nonsynonymous and synonymous molecular clocks. Sixty-eight
percent of gene families rejected a nonsynonymous molecular clock, and 52% of gene families rejected a synonymous molecular
clock. Thus, most gene families in this study deviated from clock-like evolution at either synonymous or nonsynonymous sites.
Third, we calculated the effective number of codons and the proportion of G+C synonymous sites for each sequence in each gene
family. One or both quantities vary significantly within 18 of 25 gene families. Finally, we tested for gene conversion, and
only six gene families provided evidence of gene conversion events. Altogether, evolution for these 25 gene families is marked
by selective constraint that varies among gene family members, a lack of molecular clock at both synonymous and nonsynonymous
sites, and substantial variation in codon usage.
Received: 25 May 2000 / Accepted: 16 October 2000 相似文献
15.
Molecular Evolution of Cytochrome b of Subterranean Mole Rats, Spalax ehrenbergi Superspecies, in Israel 总被引:1,自引:0,他引:1
We describe the molecular evolution of cytochrome b of blind subterranean mole rats. We examined 12 individuals for nucleotide differences in the region of 402 base pairs of
mitochondrial cytochrome b. Each individual represents a different population from the entire ecological and speciational range of the four chromosomal
species in Israel (2n= 52, 54, 58, and 60) belonging to the Spalax ehrenbergi superspecies. Our results indicate the following. (i) There are seven first-position transitional differences, compared to
34 variable third positions, with no observed second-position substitutions. (ii) A maximum of four amino acids differences
occurs across the range. (iii) Within-species diversity increases southward. Only 1 autoapomorphic substitution characterizes
either 2n= 52 or 2n= 54, but 6–11 substitutions characterize 2n= 58, and 9–13 substitutions characterize 2n= 60. (iv) Both parsimony and maximum-likelihood trees suggest two monophyletic groups: (a) 2n= 52 and 54, and (b) 2n= 58 and 60, as identified earlier by other protein and DNA markers. (v) Mitochondrial cytochrome b heterogeneity is significantly correlated with climatic factors (rainfall) and biotic factors (body size and allozymes).
We hypothesize that two selective regimes direct cytochrome b evolution in the S. ehrenbergi superspecies: (i) purifying selection in the flooded, mesic, hypoxic northern range of 2n= 52 and 54 and (ii) diversifying selection in the climatically spatiotemporal, xeric, and variable southern range of 2n= 58 and 60. Thus, the molecular evolution of mitochondrial cytochrome b in S. ehrenbergi is explicable by opposite selective stresses across the range of S. ehrenbergi in Israel, associated with the ecological adaptive radiation of the complex.
Received: 23 October 1998 / Accepted: 2 May 1999 相似文献
16.
We have sequenced the cytochrome b gene of Horsfield's tarsier, Tarsius bancanus, to complete a data set of sequences for this gene from representatives of each primate infraorder. These primate cytochrome
b sequences were combined with those from representatives of three other mammalian orders (cat, whale, and rat) in an analysis
of relative evolutionary rates. The nonsynonymous nucleotide substitution rate of the cytochrome b gene has increased approximately twofold along lineages leading to simian primates compared to that of the tarsier and other
primate and nonprimate mammalian species. However, the rate of transversional substitutions at fourfold degenerate sites has
remained uniform among all lineages. This increase in the evolutionary rate of cytochrome b is similar in character and magnitude to that described previously for the cytochrome c oxidase subunit II gene. We propose that the evolutionary rate increase observed for cytochrome b and cytochrome c oxidase subunit II may underlie an episode of coadaptive evolution of these two proteins in the mitochondria of simian primates.
Received: 15 December 1997 / Accepted: 24 February 1998 相似文献
17.
Tertiary structures of proteins are conserved better than their primary structures during evolution. Quaternary structures
or subunit organizations, however, are not always conserved. A typical case is found in hemoglobin family. Although human,
Scapharca, and Urechis have tetrameric hemoglobins, their subunit contacts are completely different from each other. We report here that only one
or two amino acid replacements are enough to create a new contact between subunits. Such a small number of chance replacements
is expected during the evolution of hemoglobins. This result explains why different modes of subunit interaction evolved in
animal hemoglobins. In contrast, certain interactions between subunits are necessary for cooperative oxygen binding. Cooperative
oxygen binding is observed often in dimeric and tetrameric hemoglobins. Conformational change of a subunit induced by the
first oxygen binding to the heme group is transmitted through the subunit contacts and increases the affinity of the second
oxygen. The tetrameric hemoglobins from humans and Scapharca have cooperativity in spite of their different modes of subunit contact, but the one from Urechis does not. The relationship between cooperativity and the mode of subunit contacts is not clear. We compared the atomic interactions
at the subunit contact surface of cooperative and non-cooperative tetrameric hemoglobins. We show that heme-contact modules
M3–M6 play a key role in the subunit contacts responsible for cooperativity. A module was defined as a contiguous peptide
segment having compact conformation and its average length is about 15 amino acid residues. We show that the cooperative hemoglobins
have interactins involving at least two pairs of modules among the four heme-contact modules at subunit contact.
Received: 12 January 2001 / Accepted: 3 April 2001 相似文献
18.
We characterized a full-length gene encoding wild silkmoth Antheraea pernyi fibroin (Ap-fibroin) to clarify the conformation of repetitive sequences. The gene consisted of a first exon encoding 14
amino acid residues, a short intron (120 bp), and a long second exon encoding 2,625 amino acid residues. Three amino acids,
alanine, glycine, and serine, amounted to 81% of the Ap-fibroin sequence. The Ap-fibroin, except for 155 residues of the amino
terminus, was composed of 80 tandemly arranged polyalanine-containing units (motifs). A motif was a doublet of a polyalanine
block (PAB) and a nonpolyalanine block (NPAB). Seventy-eight of the 80 motifs were classified into four types based on differences
in the NPAB sequences. Although respective motifs were significantly conserved, many rearrangements were observed within the
second exon, i.e., the triplication of a 558-bp-long sequence and other duplication events of shorter sequences. Chi-like
sequences, GCTGGAG, might contribute to the rearrangement within the gene as described in human minisatellite loci, because
they were found at specific sites of NPAB-encoding sequences in three of four types of motifs. The present results support
the idea that the Ap-fibroin gene is unstable like minisatellite sequences and that the evolution of this gene is strongly
associated with its instability.
Received: 18 February 2000 / Accepted: 30 June 2000 相似文献
19.
Cristina M. Justice Zhining Den Son V. Nguyen Mark Stoneking Prescott L. Deininger Mark A. Batzer Bronya J.B. Keats 《Journal of molecular evolution》2001,52(3):232-238
Friedreich ataxia is an autosomal recessive neurodegenerative disorder associated with a GAA repeat expansion in the first
intron of the gene (FRDA) encoding a novel, highly conserved, 210 amino acid protein known as frataxin. Normal variation in
repeat size was determined by analysis of more than 600 DNA samples from seven human populations. This analysis showed that
the most frequent allele had nine GAA repeats, and no alleles with fewer than five GAA repeats were found. The European and
Syrian populations had the highest percentage of alleles with 10 or more GAA repeats, while the Papua New Guinea population
did not have any alleles carrying more than 10 GAA repeats. The distributions of repeat sizes in the European, Syrian, and
African American populations were significantly different from those in the Asian and Papua New Guinea populations (p < 0.001). The GAA repeat size was also determined in five nonhuman primates. Samples from 10 chimpanzees, 3 orangutans, 1
gorilla, 1 rhesus macaque, 1 mangabey, and 1 tamarin were analyzed. Among those primates belonging to the Pongidae family,
the chimpanzees were found to carry three or four GAA repeats, the orangutans had four or five GAA repeats, and the gorilla
carried three GAA repeats. In primates belonging to the Cercopithecidae family, three GAA repeats were found in the mangabey
and two in the rhesus macaque. However, an AluY subfamily member inserted in the poly(A) tract preceding the GAA repeat region in the rhesus macaque, making the amplified
sequence approximately 300 bp longer. The GAA repeat was also found in the tamarin, suggesting that it arose at least 40 million
years ago and remained relatively small throughout the majority of primate evolution, with a punctuated expansion in the human
genome.
Received: 18 August 2000 / Accepted: 10 November 2000 相似文献
20.
The aminoacyl-tRNA synthetases are ubiquitous enzymes which catalyze a crucial step of the cell life, the specific attachment
of amino acids to their cognate tRNA. The amino acid sequences of three archaeal seryl-tRNA synthetases (SerRS) from Haloarcula marismortui and Methanococcus jannaschii, both belonging to the group of Euryarchaeota, and from Sulfolobus solfataricus, of the group of Crenarchaeota, were aligned with other eubacterial and eukaryal available SerRS sequences. In an attempt to identify some features of adaptation
to extreme environments of these organisms, amino acid composition and amino acid substitutions between mesophilic and thermophilic
SerRS were analyzed. In addition, universal phylogenetic trees of SerRS including the three known archaeal sequences, rooted
by the threonyl-tRNA synthetases were inferred. Amino acid analyses of the SerRS revealed two ways of adaptation to thermophilic
environments between the Eubacteria and the Archaea; most of the usually described amino acid substitutions were nonsignificant in the case of archaeal thermophilic SerRS and
most amino acid composition biases seemed to be linked to the genome G+C content pressure. The phylogenetic analysis of the
SerRS showed the Archaea to be paraphyletic, H. marismortui emerging with the Gram-positive Bacteria, M. jannaschii being near the root of the tree, and S. solfataricus branching with Eucarya.
Received: 30 March 1998 / Accepted: 14 July 1998 相似文献