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At least 955 records · Page 53Linked to original sources
PubMed1991

Molecular evolution of the urate oxidase-encoding gene in hominoid primates: nonsense mutations.

Nucleotide sequences of portions of second and fifth exons of urate oxidase encoding gene (UOX) of chimpanzee, gorilla, orangutan, rhesus monkey and squirrel monkey obtained following amplification by polymerase chain reaction have been compared with corresponding sequences of human, baboon and rat UOX. Two or more nonsense mutations are found in the coding regions of this UOX gene thus far analyzed in human, chimpanzee, gorilla and orangutan, but not in the baboon, rhesus monkey and squirrel monkey. Of these nonsense mutations, the stop codon at amino acid position 33 is constant in the human and the three great apes suggesting that this may be the original mutation responsible for the inactivation of the UOX gene during hominoid evolution.

Amino Acid Sequence↗
PubMed1988

The molecular evolution of genes and proteins: a tale of two serines.

The advent of techniques for cloning and rapidly sequencing DNA has produced an explosive increase of sequence information for nucleic acids and their inferred proteins. Careful study of this large store of data might give us new insights into the relations between the linear sequences of genes and their functions embodied in the three-dimensional structure of proteins, and also illuminate the origin and evolution of the structural complexity of present-day proteins. Here I argue from such a study that the active site sequences of enzymes that have analogous essential serine residues lie in fact on two lines of descent from an ancient ancestral enzyme which had a cysteine instead of serine in its active site. This is based on the assumption that the two codon types which define the separate lines of descent and which have different bases in two positions could not interconvert by single mutations.

Amino Acid Sequence↗
PubMed1990

Structural design and molecular evolution of a cytokine receptor superfamily.

A family of cytokine receptors comprising molecules specific for a diverse group of hematopoietic factors and growth hormones has been principally defined by a striking homology of binding domains. This work proposes that the approximately 200-residue binding segment of the canonical cytokine receptor is composed of two discrete folding domains that share a significant sequence and structural resemblance. Analogous motifs are found in tandem approximately 100-amino acid domains in the extracellular segments of a receptor family formed by the interferon-alpha/beta and -gamma receptors and tissue factor, a membrane tether for a coagulation protease. Domains from the receptor supergroup reveal clear evolutionary links to fibronectin type III structures, approximately 90-amino acid modules that are typically found in cell surface molecules with adhesive functions. Predictive structural analysis of the shared receptor and fibronectin domains locates seven beta-strands in conserved regions of the chain; these strands are modeled to fold into antiparallel beta-sandwiches with a topology that is similar to immunoglobulin constant domains. These findings have strong implications for understanding the evolutionary emergence of an important class of regulatory molecules from primitive adhesive modules. In addition, the resulting double-barrel design of the receptors and the spatial clustering of conserved residues suggest a likely binding site for cytokine ligands.

Amino Acid Sequence↗
PubMed1988

Molecular evolution of the Escherichia coli chromosome. I. Analysis of structure and natural variation in a previously uncharacterized region between trp and tonB.

We present the sequence of a 3500-bp region of the Escherichia coli strain K12 chromosome lying between the tryptophan operon and the tonB gene. Analysis of the sequence yields six open reading frames that have properties characteristic of genes for proteins. The reading frames are closely spaced, and putative transcription units and control sites compose over 95% of the DNA. The sequences of several wild strains of E. coli have been determined for a large segment of the region described. Comparison of these sequences reveals the effects of base substitutions, DNA rearrangements, and recombination. In the regions presumably expressed as polypeptides, most of the natural variation results from synonymous substitutions. However, the DNA rearrangements identified have end points within the open reading frames and disrupt them in a variety of ways. The effects of genetic recombination between strains, recently found to be significant on a large scale in E. coli, are also apparent in the region between trp and tonB.

Base Sequence↗
PubMed2000

Molecular evolution of a type 1 wild-vaccine poliovirus recombinant during widespread circulation in China.

Type 1 wild-vaccine recombinant polioviruses were isolated from poliomyelitis patients in China from 1991 to 1993. We compared the sequences of 34 recombinant isolates over the 1,353-nucleotide (nt) genomic interval (nt 2480 to 3832) encoding the major capsid protein, VP1, and the protease, 2A. All recombinants had a 367-nt block of sequence (nt 3271 to 3637) derived from the Sabin 1 oral poliovirus vaccine strain spanning the 3'-terminal sequences of VP1 (115 nt) and the 5' half of 2A (252 nt). The remaining VP1 sequences were closely (up to 99.5%) related to those of a major genotype of wild type 1 poliovirus endemic to China up to 1994. In contrast, the non-vaccine-derived sequences at the 3' half of 2A were more distantly related (<90% nucleotide sequence match) to those of other contemporary wild polioviruses from China. The vaccine-derived sequences of the earliest (April 1991) isolates completely matched those of Sabin 1. Later isolates diverged from the early isolates primarily by accumulation of synonymous base substitutions (at a rate of approximately 3.7 x 10(-2) substitutions per synonymous site per year) over the entire VP1-2A interval. Distinct evolutionary lineages were found in different Chinese provinces. From the combined epidemiologic and evolutionary analyses, we propose that the recombinant virus arose during mixed infection of a single individual in northern China in early 1991 and that its progeny spread by multiple independent chains of transmission into some of the most populous areas of China within a year of the initiating infection.

Base Sequence↗
PubMed1989

The neutral theory of molecular evolution and the world view of the neutralists.

The main tenet of the neutral theory is that the great majority of evolutionary changes at the molecular level are caused not by Darwinian selection but by random fixation of selectively neutral (or very nearly neutral) alleles through random sampling drift under continued mutation pressure. The theory also asserts that the majority of protein and DNA polymorphisms are selectively neutral, and that they are maintained in the species by mutational input balanced by random extinction rather than by "balancing selection." The neutral theory is based on simple assumptions. This enabled us to develop mathematical theories (using the diffusion equation method) that can treat these phenomena in quantitative terms and that permit theory to be tested against actual observations. Although the neutral theory has been severely criticized by the neo-Darwinian establishment, supporting evidence has accumulated over the last 20 years. In particular, the recent burst of DNA sequence data helped to strengthen the theory a great deal. I believe that the neutral theory triggered reexamination of the traditional "synthetic theory of evolution." In this paper, I review the present status of the neutral theory, including discussions of such topics as "molecular evolutionary clock," very high evolutionary rates observed in RNA viruses, a deviant coding system found in Mycoplasm together with the concept of mutation-driven neutral evolution, and the origin of life. I also present a worldview based on the conception of what I call "survival of the luckiest."

Animals↗
PubMed1993

Region-specific rates of molecular evolution: a fourfold reduction in the rate of accumulation of "silent" mutations in transcribed versus nontranscribed regions of homologous DNA fragments derived from two closely related mouse species.

We have sequenced homologous DNA fragments of 2.7 and 2.8 kbp derived from the closely related mouse species Mus musculus domesticus (M. domesticus) and Mus musculus musculus (M. musculus), respectively. These two species diverged approximately 1 million years ago. Each DNA fragment contains 1.35 kbp of the 3' end of the constitutively expressed 2.2-kbp aprt (adenine phosphoribosyltransferase) gene and a similarly sized nontranscribed region downstream of the aprt gene. The aprt gene region contains protein coding sequences (0.35 kbp), intronic sequences (0.75 kbp), and a 3' nontranslated sequence (0.25 kbp). Both the M. domesticus and M. musculus downstream regions share three partial copies of the B1 repetitive element with the M. musculus downstream region containing an additional complete copy of this element. A comparison of the 2.7- and 2.8-kbp DNA fragments revealed a total of 63 molecular alterations (i.e., mutations) that were approximately fourfold more abundant in the nontranscribed downstream region than in the transcribed aprt gene. Of the 11 mutations observed in the transcribed region, 7 were found in introns, 3 in the 3' untranslated sequence, and 1 was a synonymous change in an exon. A comparison of the human and M. domesticus aprt genes has previously revealed no homology in either the intronic or 3' nontranslated regions with the exception of a 26-bp sequence in intron 3 and sequences at the exon/intron boundaries necessary for correct mRNA splicing (Broderick et al., Proc. Natl. Acad. Sci. USA, 84:3349, 1987). Therefore, there does not appear to be selective pressure for sequences within these regions. We conclude that there is a lower rate of accumulation of "silent" mutations in the transcribed mouse aprt gene than in a contiguous nontranscribed downstream region. A possible molecular mechanism involving preferential DNA repair for the transcribed region is discussed.

Adenine Phosphoribosyltransferase↗
PubMed1999

The molecular evolution of trypanosomes.

The absence of a fossil record has meant that the evolution of protozoa has remained largely a matter for speculation. Recent advances in molecular biology and phylogenetic analysis, however, are allowing the 'history written in the genes' to be interpreted. Here, Jamie Stevens and Wendy Gibson review progress in reconstruction of trypanosome phylogeny based on molecular data from rRNA and protein-coding genes.

Africa↗
PubMed1987

Molecular evolution of serpins: homologous structure of the human alpha 1-antichymotrypsin and alpha 1-antitrypsin genes.

alpha 1-Antichymotrypsin belongs to a supergene family that includes alpha 1-antitrypsin, antithrombin III, ovalbumin, and angiotensinogen. The human chromosomal alpha 1-antichymotrypsin gene has been cloned and its molecular structure established. The gene is approximately 12 kb in length and contains five exons and four introns. The locations of the introns within the alpha 1-antichymotrypsin gene are identical with those of the human alpha 1-antitrypsin and angiotensinogen genes. Other members of this supergene family contain introns located at nonhomologous positions of the genes. The homologous organization of the alpha 1-antichymotrypsin and alpha 1-antitrypsin genes corresponds with the high degree of homology between their protein sequences and suggests that these loci arose by recent gene duplication. A model is presented for the evolution of both the genomic structure and the protein sequences of the serine protease inhibitor superfamily.

Animals↗
PubMed1989

Molecular evolution of the small subunit of ribulose bisphosphate carboxylase: nucleotide substitution and gene conversion.

The nucleotide sequences encoding the mature portion of 31 ribulose 1.5-bisphosphate carboxylase small subunit (SSU) genes from 17 genera of plants, green algae and cyanobacteria were examined. Among the 465 pairwise sequence comparisons, SSU multigene family members within the same species were more similar to each other in nonsynonymous or replacement nucleotide substitutions (RNS) than they were to SSU sequences in any other organism. The concerted evolution of independent SSU gene lineages within closely related plant species suggests that homogenization of RNS positions has occurred at least once in the life of each genus. The rate of expected RNS among mature SSU sequences was calculated to be 1.25 X 10(-9)/site/yr for the first 70 million years (MY) of divergence with a significant slowing to 0.13 X 10(-9)/site/yr for the next 1,400 MY. The data suggest that mature SSU sequences do not accumulate more than 20% differences in the RNS positions without compensatory changes in other components of this enzyme system. During the first 70 MY of divergence between species, the rate of expected synonymous or silent nucleotide substitutions (SNS) is approximately 6.6 X 10(-9)/site/yr. This is five times the RNS rate and is similar to the silent rate observed in animals. In striking contrast, SNS and RNS do not show this correlation among SSU gene family members within a species. A mechanism involving gene conversion within the exons followed by selection for biased gene conversion products with conservation of RNS positions and divergence of SNS positions is discussed. A SSU gene tree based on corrected RNS for 31 SSU sequences is presented and agrees well with a species tree based on morphological and cytogenetic traits for the 17 genera examined. SSU gene comparisons may be useful in predicting phylogenetic relationships and in some cases divergence times of various plant, algal and cyanobacterial species.

Amino Acid Sequence↗
PubMed1986

Molecular evolution of mammalian lactate dehydrogenase-A genes and pseudogenes: association of a mouse processed pseudogene with a B1 repetitive sequence.

A mouse genomic clone containing a lactate dehydrogenase-A (LDH-A) processed pseudogene and a B1 repetitive element was isolated, and a nucleotide sequence of approximately 3 kb was determined. The pseudogene and B1 element are flanked by perfect 13-bp repeats, and the B1 sequence starts at 14 nucleotides 3' to the presumptive polyadenylation signal of the pseudogene. The nucleotide sequences of the LDH-A genes and processed pseudogenes from mouse, rat, and human were compared, and a phylogenetic tree was constructed. The rate and pattern of nucleotide substitutions in the LDH-A pseudogenes are similar to previously reported results (Li et al. 1984). The average rate of nucleotide substitutions in the LDH-A pseudogenes is 4.3 X 10(-9)/site/year. The substitutions of C----T and G----A are most frequent, and A----G substitutions are relatively high. The rate of synonymous substitutions in the LDH-A genes is 5.3 X 10(-9), which is not significantly higher than the average rate of 4.7 X 10(-9) for 35 mammalian genes. The rate of nonsynonymous substitutions in the LDH-A genes is 0.20 X 10(-9), which is considerably lower than the average rate of 0.88 X 10(-9) for 35 mammalian genes. Thus, the mammalian LDH-A gene appears to be highly conserved in evolution.

Animals↗
PubMed1990

Molecular evolution from argininosuccinate lyase to delta-crystallin.

cDNA clones for rat argininosuccinate lyase, a urea cycle enzyme, were cloned and amino acid sequence of the enzyme was predicted. The rat enzyme is 54% identical with the yeast enzyme, which is involved in arginine biosynthesis, thereby indicating that this urea cycle enzyme evolved from the arginine biosynthetic enzyme. A striking similarity (64% identity) was found between amino acid sequences of rat argininosuccinate lyase and chicken delta-crystallin, a major structural protein of the eye lens. The gene for the rat argininosuccinate lyase was cloned and its structure was determined. This gene is a single-copy gene about 14 kilobases long and is split into 16 exons. A comparison with chicken delta-crystallin genes revealed that all introns interrupt the protein-coding regions at homologous positions. This close similarity in structural organization provides strong evidence for the view that the chicken delta 1- and delta 2-crystallin genes evolved by recruitment and duplication of the preexisting argininosuccinate lyase gene and that delta 2-crystallin is probably the direct homologue of argininosuccinate lyase.

Amino Acid Sequence↗
PubMed1991

Molecular evolution of the psi eta-globin gene locus: gibbon phylogeny and the hominoid slowdown.

An 8.4-kb genomic region spanning both the psi eta-globin gene locus and flanking DNA was sequenced from the common gibbon (Hylobates lar). In addition, sequencing of the entire orthologous region from galago (Galago crassicaudatus) was completed. The gibbon and galago sequences, along with published orthologous sequences from 10 other species, were aligned. These noncoding nucleotide sequences represented four human alleles, four apes (chimpanzee, gorilla, organgutan, and gibbon), an Old World monkey (rhesus monkey), two New World monkeys (spider and owl monkeys), tarsier, two strepsirhines (galago and lemur), and goat. Divergence and maximum parsimony analyses of the psi eta genomic region first groups humans and chimpanzees and then, at progressively more ancient branch points, successively joins gorillas, orangutans, gibbons, Old World monkeys, New World monkeys, tarsiers, and strepsirhines (the lemuriform-lorisiform branch of primates). This cladistic pattern supports the taxonomic grouping of all extant hominoids into family Hominidae, the division of Hominidae into subfamilies Hylobatinae (gibbons) and Homininae, the division of Homininae into tribes Pongini (orangutans) and Hominini, and the division of Hominini into subtribes Gorillina (gorillas) and Hominina (chimpanzees and humans). The additional gibbon and galago sequence data provide further support for the occurrence of a graded evolutionary-rate slowdown in the descent of simian primates, with the slowing rate being more pronounced in the great-ape and human lineages than in the gibbon or monkey lineages. A comparison of global versus local molecular clocks reveals that local clock predictions, when focused on a specific number of species within a narrow time frame, provide a more accurate estimate of divergence dates than do those of global clocks.

Animals↗