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PubMed1999

Genomic organization and chromosomal localization of the human cathepsin L2 gene.

Cathepsin L2 is a recently described cysteine proteinase with high sequence homology to cathepsin L and other members of the papain superfamily of cysteine proteinases. Its expression is regulated in a tissue-specific manner and is high in thymus, testis and cornea. In the present study, the entire gene sequence, including 5' and 3' flanking region, and chromosomal localization of human cathepsin L2 were determined. The gene spans approximately 6.4 kb and consists of eight exons and seven introns. Genomic organization was similar to human cathepsin L and more than 50% similarity was found between the first introns of cathepsin L and L2, suggesting that they diverged late in evolution. The transcription initiation site, determined by primer extension, was 198 nucleotides from the first ATG. The 5' flanking region lacks a TATA box but has one SP1 site. The gene was mapped to chromosome 9q21-22 by fluorescence in situ hybridization and the distance from cathepsin L was determined to be 15 cM by compiling radiation hybrid mapping results with a genetic map.

Base Sequence↗
PubMed2003

Quantitative trait loci responsible for variation in sexually dimorphic traits in Drosophila melanogaster.

To understand the mechanisms of morphological evolution and species divergence, it is essential to elucidate the genetic basis of variation in natural populations. Sexually dimorphic characters, which evolve rapidly both within and among species, present attractive models for addressing these questions. In this report, we map quantitative trait loci (QTL) responsible for variation in sexually dimorphic traits (abdominal pigmentation and the number of ventral abdominal bristles and sex comb teeth) in a natural population of Drosophila melanogaster. To capture the pattern of genetic variation present in the wild, a panel of recombinant inbred lines was created from two heterozygous flies taken directly from nature. High-resolution mapping was made possible by cytological markers at the average density of one per 2 cM. We have used a new Bayesian algorithm that allows QTL mapping based on all markers simultaneously. With this approach, we were able to detect small-effect QTL that were not evident in single-marker analyses. Our results show that at least for some sexually dimorphic traits, a small number of QTL account for the majority of genetic variation. The three strongest QTL account for >60% of variation in the number of ventral abdominal bristles. Strikingly, a single QTL accounts for almost 60% of variation in female abdominal pigmentation. This QTL maps to the chromosomal region that Robertson et al. have found to affect female abdominal pigmentation in other populations of D. melanogaster. Using quantitative complementation tests, we demonstrate that this QTL is allelic to the bric a brac gene, whose expression has previously been shown to correlate with interspecific differences in pigmentation. Multiple bab alleles that confer distinct phenotypes appear to segregate in natural populations at appreciable frequencies, suggesting that intraspecific and interspecific variation in abdominal pigmentation may share a similar genetic basis.

Animals↗
PubMed1998

Genomic organization and chromosomal localization of three members of the UDP-N-acetylgalactosamine: polypeptide N-acetylgalactosaminyltransferase family.

A homologous family of UDP- N -acetylgalactosamine: polypeptide N -acetylgalactosaminyltransferases (GalNAc-transferases) initiate O-glycosylation. These transferases share overall amino acid sequence similarities of approximately 45-50%, but segments with higher similarities of approximately 80% are found in the putative catalytic domain. Here we have characterized the genomic organization of the coding regions of three GalNAc-transferase genes and determined their chromosomal localization. The coding regions of GALNT1 , -T2 , and -T3 were found to span 11, 16, and 10 exons, respectively. Several intron/exon boundaries were conserved within the three genes. One conserved boundary was shared in a homologous C. elegans GalNAc-transferase gene. Fluorescence in situ hybridization showed that GALNT1 , -T2 , and -T3 are localized at chromosomes 18q12-q21, 1q41-q42, and 2q24-q31, respectively. These results suggest that the members of the polypeptide GalNAc-transferase family diverged early in evolution from a common ancestral gene through gene duplication.

Amino Acid Sequence↗
PubMed2003

Evidence for cocladogenesis between diverse dictyopteran lineages and their intracellular endosymbionts.

Bacteria of the genus Blattabacterium are intracellular symbionts that reside in specialized cells of cockroaches and the termite Mastotermes darwiniensis. They appear to be obligate mutualists, and are transmitted vertically in the eggs. Such characteristics are expected to lead to equivalent phylogenies for host and symbiont, and we tested this hypothesis using recently accumulated data on relationships among termites and cockroaches and their Blattabacterium spp. Host and symbiont topologies were found to be highly similar, and various tests indicated that they were not statistically different. A close relationship between endosymbionts from termites and members of the wood-feeding cockroach genus Cryptocercus was found, supporting the hypothesis that the former evolved from subsocial, wood-dwelling cockroaches. The majority of the Blattabacterium spp. sequences appear to have undergone similar rates of evolution since their divergence from a common ancestor, and an estimate of this rate was determined based on early Cretaceous host fossils. The results support the idea that the stem group of modern cockroaches radiated sometime between the late Jurassic and early Cretaceous-not the Carboniferous, as has been suggested on the basis of roach-like fossils from this epoch.

Animals↗
PubMed1991

Genomic organization of the retinoic acid receptor gamma gene.

The retinoic acid receptors (RAR) belong to the large family of ligand responsive gene regulatory proteins that includes receptors for steroid and thyroid hormones. These proteins contain two highly conserved domains, involved in determining their DNA and ligand binding activities. Three distinct RARs have been identified (RAR alpha, beta, and gamma) which are encoded by genes on separate chromosomes. Additional isoforms of the three receptors have been described that all differ in the N-terminal regions. To gain insight into the genomic organization and mechanisms of RAR isoform generation, we have analyzed the genomic structure of the RAR gamma gene. The major portion of the RAR gamma protein, including DNA and ligand binding domains, is encoded by seven exons that are identical for all RARg isoforms and are represented by a relatively small portion of the RAR gamma gene. The major portion of this gene encodes separate N-terminal exons for gamma 1 and gamma 2 isoforms and several exons for gamma 1 untranslated regions. We show that RAR gamma 2 transcription is regulated by its own promoter. In comparison with the steroid receptor subfamily, various splice sites of RAR gamma occur at altered positions, suggesting that the RAR subfamily has diverged early during evolution.

Amino Acid Sequence↗
PubMed1998

Similarities and differences among 105 members of the Int family of site-specific recombinases.

Alignments of 105 site-specific recombinases belonging to the Int family of proteins identified extended areas of similarity and three types of structural differences. In addition to the previously recognized conservation of the tetrad R-H-R-Y, located in boxes I and II, several newly identified sequence patches include charged amino acids that are highly conserved and a specific pattern of buried residues contributing to the overall protein fold. With some notable exceptions, unconserved regions correspond to loops in the crystal structures of the catalytic domains of lambda Int (Int c170) and HP1 Int (HPC) and of the recombinases XerD and Cre. Two structured regions also harbor some pronounced differences. The first comprises beta-sheets 4 and 5, alpha-helix D and the adjacent loop connecting it to alpha-helix E: two Ints of phages infecting thermophilic bacteria are missing this region altogether; the crystal structures of HPC, XerD and Cre reveal a lack of beta-sheets 4 and 5; Cre displays two additional beta-sheets following alpha-helix D; five recombinases carry large insertions. The second involves the catalytic tyrosine and is seen in a comparison of the four crystal structures. The yeast recombinases can theoretically be fitted to the Int fold, but the overall differences, involving changes in spacing as well as in motif structure, are more substantial than seen in most other proteins. The phenotypes of mutations compiled from several proteins are correlated with the available structural information and structure-function relationships are discussed. In addition, a few prokaryotic and eukaryotic enzymes with partial homology with the Int family of recombinases may be distantly related, either through divergent or convergent evolution. These include a restriction enzyme and a subgroup of eukaryotic RNA helicases (D-E-A-D proteins).

Amino Acid Sequence↗
PubMed1981

Skeletal muscle actin mRNA. Characterization of the 3' untranslated region.

Plasmids p749, p106, and p150 contain cDNA inserts complementary to rat skeletal muscle actin mRNA. Nucleotide sequence analysis indicates the following sequence relationships: p749 specifies codons 171 to 360; p150 specifies codons 357 to 374 together with 120 nucleotides of the 3'-non-translated region; p106 specifies the last actin amino acid codon, the termination codon and the entire 3' non-translated region. Plasmid p749 hybridized with RNA extracted from rat skeletal muscle, cardiac muscle, smooth (stomach) muscle, and from brain. It also hybridizes well with RNA extracted from skeletal muscle and brain of dog and chick. Plasmid p106 hybridized specifically with rat striated muscles (skeletal and cardiac muscle) mRNA but not with mRNA from rat stomach and from rat brain. It also hybridized to RNA extracted from skeletal muscle of rabbit and dog but not from chick. Thermal stability of the hybrids and sensitivity to S1 digestion also indicated substantial divergence between the 3' untranslated end of rat and dog skeletal muscle actins. The investigation shows that the coding regions of actin genes are highly conserved, whereas the 3' non-coding regions diverged considerably during evolution. Probes constructed from the 3' non-coding regions of actin mRNAs can be used to identify the various actin mRNA and actin genes.

Actins↗
PubMed2000

Molecular cloning of cDNA encoding two subunits of calcineurin from scallop testis: demonstration of stage-specific expression during maturation of the testis.

Complementary DNAs encoding two subunits of scallop (Patinopecten yessoensis) testis calcineurin were cloned, and the nucleotide sequences of their coding regions were determined. The deduced amino acid sequences of the catalytic subunit, calcineurin A (486 amino acid residues, M(r) 55,005.91), and the regulatory subunit, calcineurin B (170 residues, M(r) 19,237.67), showed high similarity to those of mammalian calcineurins, especially to the brain-type ones rather than to the testis-specific isoforms. Northern blot analysis showed that only a single species for each subunit was expressed in testis and the expression of each subunit increased dramatically from January to March during the maturation stages of the one-year cycle. The period when the maximum amount of mRNAs for calcineurin was expressed corresponds to the one immediately after meiosis, that is, the maturation stage in which 20-80% of the average testis is occupied by spermatozoa. The result is consistent with the one as to the expression of the testis-specific isoform of calcineurin A in mouse, which occurs immediately after meiosis. This is the first report on the stage-specific expression of calcineurin in invertebrate testis and its sequence similarity to the mammalian brain-type isoforms may indicate that the mammalian testis-specific isoforms appeared in evolution after the divergence of mammals from the mollusks and then diverged rapidly for specific functions in testis.

Amino Acid Sequence↗
PubMed1994

Structural organization of the mouse glycophorin A gene.

The human glycophorin gene has been extensively studied, but information on the homologous gene from other species has been unavailable. Here, we determined the structural organization of mouse glycophorin A gene and compared it with the human gene. The mouse glycophorin gene is a single copy gene while in humans, there are two highly related genes (A and B) that were generated by homologous recombination. Chromosomal mapping indicated that the mouse gene is located in the central region of the mouse chromosome 8, which is syntenic with human chromosomes 4q28-31 where the human glycophorin A gene has been mapped. The mouse gene consists of 8 exons, while the human gene consists of 7 exons and the length of each exon is quite short except for the last exon. The last 4 exons showed extensive homology between the mouse and human genes but divergence in the 5'-exons of the two genes was high. The results suggest that glycophorin genes of mouse and human may have been generated from the same ancestor, but diverged greatly during evolution. The upstream regulatory region of the mouse gene consists of multiple motifs for DNA binding factors that may be required for its erythroid-specific expression.

Animals↗
PubMed2002

Natural selection on the erythrocyte surface.

Surface glycoproteins are principal receptors used by pathogens to invade target cells. It has been suggested that mammalian erythrocyte surface glycoproteins function as decoy receptors attracting pathogens to the anucleated erythrocyte and away from their target tissues. Glycophorin A (GYPA) is solely expressed on the erythrocyte surface where it is the most abundant sialoglycoprotein, although its function is unknown. The pathogen decoy hypothesis may be relevant here, as GYPA has been shown in vitro to bind numerous viruses and bacteria, which do not infect erythrocytes. However, it is also a receptor for erythrocyte invasion by the malarial parasite Plasmodium falciparum. Analyses of gypa sequence variation among six higher primates and within a human population show that there is a large excess of replacement (nonsynonymous) substitutions along each primate lineage (particularly on exons 2-4 encoding the extracellular glycosylated domain of GYPA) and a significant excess of polymorphisms in exon 2 (encoding the terminal portion of the extracellular domain) within humans. These two signatures suggest that there has been exceptionally strong positive selection on this receptor driving GYPA divergence during primate evolution and balancing selection maintaining allelic variation within human populations. The pathogen decoy hypothesis alone is adequate to explain both these signatures of between-species and within-species diversifying selection. This has implications for understanding the functions of erythrocyte surface components and their roles in health and disease.

Alleles↗
PubMed1994

Protein phylogeny gives a robust estimation for early divergences of eukaryotes: phylogenetic place of a mitochondria-lacking protozoan, Giardia lamblia.

A partial nucleotide sequence of the mRNA encoding a major part of elongation factor 1 alpha (EF1 alpha) from a mitochondria-lacking protozoan, Giardia lamblia, was reported, and the phylogenetic relationship among lower eukaryotes was inferred by the maximum-likelihood and maximum-parsimony methods of protein phylogeny. Both the methods consistently demonstrated that, G. lamblia among the four protozoan species being analyzed, is the earliest offshoot of the eukaryotic tree. Although the Giardia EF1 alpha gene showed an extremely high G+C content as compared with those of other protozoa, it was concentrated only at the third codon positions, resulting in no remarkable differences of amino acid frequencies vis-à-vis those of other species. This clearly suggests (a) that the amino acid frequencies of conservative proteins are free from the drastic bias of genome G+C content, which is a serious problem in the widely used tree of ribosomal RNA, and (b) that protein phylogeny gives a robust estimation for the early divergences in the evolution of eukaryotes.

Amino Acid Sequence↗
PubMed1988

Complete sequences of the rRNA genes of Drosophila melanogaster.

In this, the first of three papers, we present the sequence of the ribosomal RNA (rRNA) genes of Drosophila melanogaster. The gene regions of D. melanogaster rDNA encode four individual rRNAs: 18S (1,995 nt), 5.8S (123 nt), 2S (30 nt), and 28S (3,945 nt). The ribosomal DNA (rDNA) repeat of D. melanogaster is AT rich (65.9% overall), with the spacers being particularly AT rich. Analysis of DNA simplicity reveals that, in contrast to the intergenic spacer (IGS) and the external transcribed spacer (ETS), most of the rRNA gene regions have been refractory to the action of slippage-like events, with the exception of the 28S rRNA gene expansion segments. It would seem that the 28S rRNA can accommodate the products of slippage-like events without loss of activity. In the following two papers we analyze the effects of sequence divergence on the evolution of (1) the 28S gene "expansion segments" and (2) the 28S and 18S rRNA secondary structures among eukaryotic species, respectively. Our detailed analyses reveal, in addition to unequal crossing-over, (1) the involvement of slippage and biased mutation in the evolution of the rDNA multigene family and (2) the molecular coevolution of both expansion segments and the nucleotides involved with compensatory changes required to maintain secondary structures of RNA.

Animals↗
PubMed2000

Renal cell carcinoma with rhabdoid features.

Neoplasms with rhabdoid features have been reported at many anatomic sites. In the kidney, rhabdoid tumors are typically found in children, whereas only rare examples have been reported in adults. Little is known of renal cell carcinomas (RCCs) that exhibit rhabdoid features. The objective of this study was to determine the incidence of RCC with rhabdoid attributes and characterize the histologic, immunophenotypic, and ultrastructural features by retrospective analysis of 480 consecutively identified cases of RCC in radical nephrectomy specimens. Immunohistochemical evaluation was performed in cases with rhabdoid foci using a panel of antibodies to pancytokeratin (pan-CK), CK7, CK20, epithelial membrane antigen (EMA), S-100 protein, desmin, vimentin, neuron-specific enolase (NSE), muscle-specific actin (MSA), smooth muscle actin (SMA), human melanoma, black-45 (HMB-45), and glial fibrillary acidic protein (GFAP). Electron microscopy was also performed in selected cases. The presence and extent of rhabdoid foci in relation to pathologic stage and grade were assessed. Twenty-three of 480 cases of RCC (4.7%) exhibited rhabdoid features. The 23 patients were all adults with a mean age of 61.8 years (age range, 33-84 yrs). Fifteen of the patients were men and eight were women. Histologically, the rhabdoid foci were typified by sheets and clusters of variably cohesive, large epithelioid cells with vesicular and often eccentric nuclei, prominent nucleoli, and large, paranuclear intracytoplasmic hyaline globules (inclusions). The presence of these rhabdoid features was related to high histologic Fuhrman grade of the nonrhabdoid carcinoma component, with an incidence of 0 of 84 grade I cases, eight of 300 grade 2 cases (2.6%), six of 70 grade 3 cases (8.9%), and nine of 26 grade 4 cases (34.6%; p = 3 x 10(-9)). The rhabdoid foci were all high grade. The presence of rhabdoid foci was also found in higher stage carcinomas. A total of 52% (12 of 23) of RCC cases with rhabdoid features exhibited extrarenal extension compared with 28% (24 of 92) of contemporary RCCs without rhabdoid features (p = 0.03). The size of the rhabdoid component ranged from 1 mm to more than 2 cm and comprised 1% to 50% of the renal mass. Immunoreactivity for vimentin (100%), NSE (79%), and panCK (56%) was present in the majority of cases. Substantial percentages of cases were immunopositive for EMA (47%) and S-100 protein (37%), with minimal to no immunohistochemical reactivity for CK7 (5%), SMA (5%), CK20 (0%), desmin (0%), MSA (0%), HMB-45 (0%), and GFAP (O%). A distinctive globular, paranuclear reaction pattern was found for the cytokeratin, EMA, and vimentin immunostains. Ultrastructurally, the rhabdoid cells had paranuclear intermediate filament aggregates or paranuclear condensation of organelles, often associated with peripheral vacuolization. Adult RCCs may harbor a rhabdoid component, and these neoplasms can be regarded as "composite" tumors. Rhabdoid elements are important to identify because of their high-grade nature, and association with high stage. Adult RCC with rhabdoid elements should be distinguished from pure rhabdoid tumors of kidney, in light of their clinicopathologic differences. Rhabdoid differentiation in adult renal cell carcinoma may represent clonal divergence and/ or evolution, and emergence of a particularly aggressive element.

Adult↗
PubMed1992

Two major types of JC virus defined in progressive multifocal leukoencephalopathy brain by early and late coding region DNA sequences.

A 610-bp region of the JC virus (JCV) genome sequenced from brains of 11 progressive multifocal leukoencephalopathy (PML) patients contains 20 sites of point mutations that allow reliable classification of JCV isolates into two types. These type-determining sites were located in the region extending from position 2131 in the VP1 gene, through the intergenic region, to position 2740 in the T antigen gene. At these 20 sites the presence of different nucleotides creates two distinct patterns of substitution, with six isolates having the Type 1 pattern and five having the Type 2 pattern. Only four of the 11 isolates had 'crossovers' to the opposite type consensus DNA sequence at a small number of sites, indicating a very high type specificity. Additionally, three type-determining sites occur in the non-coding region to the left of the origin of replication. Other mutations occurred at random sites, making each strain unique, although one strain, 105, is identical to the Type 1 consensus. The JCV prototype strain Mad-1 was found to be Type 1 and differs from the consensus sequence at five sites. The other previously sequenced JCV strain, GS/B, is Type 2. At three sites out of five in the T antigen C terminus there is a type-specific amino acid substitution; however, none of the type-determining mutations in the VP1 gene cause an amino acid substitution. Comparison of each type's consensus DNA sequence to that of BK virus suggests that Type 2 represents the ancestral JCV sequence from which Type 1 diverged during human evolution.

Antigens, Polyomavirus Transforming↗
PubMed1999

Characterization of two divergent endo-beta-1,4-glucanase cDNA clones highly expressed in the nonclimacteric strawberry fruit.

Two cDNAs clones (Cel1 and Cel2) encoding divergent endo-beta-1, 4-glucanases (EGases) have been isolated from a cDNA library obtained from ripe strawberry (Fragaria x ananassa Duch) fruit. The analysis of the amino acid sequence suggests that Cel1 and Cel2 EGases have different secondary and tertiary structures and that they differ in the presence of potential N-glycosylation sites. By in vitro translation we show that Cel1 and Cel2 bear a functional signal peptide, the cleavage of which yields mature proteins of 52 and 60 kD, respectively. Phylogenetic analysis revealed that the Cel2 EGase diverged early in evolution from other plant EGases. Northern analysis showed that both EGases are highly expressed in fruit and that they have different temporal patterns of accumulation. The Cel2 EGase was expressed in green fruit, accumulating as the fruit turned from green to white and remaining at an elevated, constant level throughout fruit ripening. In contrast, the Cel1 transcript was not detected in green fruit and only a low level of expression was observed in white fruit. The level of Cel1 mRNA increased gradually during ripening, reaching a maximum in fully ripe fruit. The high levels of Cel1 and Cel2 mRNA in ripe fruit and their overlapping patterns of expression suggest that these EGases play an important role in softening during ripening. In addition, the early expression of Cel2 in green fruit, well before significant softening begins, suggests that the product of this gene may also be involved in processes other than fruit softening, e.g. cell wall expansion.

Amino Acid Sequence↗
PubMed2002

A simple test: evaluating explanations for the relative simplicity of the Edwardsiidae (Cnidaria: Anthozoa).

Many members of the cnidarian subclass Zoantharia (sea anemones, corals, and their allies) pass through a larval stage with eight complete mesenteries and without posterior musculature. This larva is usually transient, developing into an adult with 12 or more mesenteries. The adults of one family of sea anemones, the Edwardsiidae, bear the larval number and arrangement of mesenteries and lack the pedal disc seen in other sea anemones. The morphology of the Edwardsiidae has been interpreted in a number of ways: (1) the Edwardsiidae are the most basal extant zoantharian, having diverged before the evolution of additional mesenteries and basal musculature; (2) they are relatively advanced sea anemones that have secondarily simplified because they burrow in sand or mud rather than attaching to a hard substrate; or (3) edwardsiids are derived anemones that have retained a juvenile morphology through paedomorphosis. Phylogenetic analyses of small subunit ribosomal gene sequences reveal that the Edwardsiidae are derived zoantharians, nested within sea anemones. None of the proposed explanations fully explain the edwardsiid's body plan; edwardsiid anatomy is a mosaic of retained primitive and derived features. The results of the present study provide insight into zoantharian phylogeny and illustrate how phylogenetic tests can be used to study the evolution of cnidarian body plans.

Animals↗
PubMed1988

The tropical African latrine blowfly, Chrysomya putoria (Wiedemann).

The status of the tropical African latrine blowfly Chrysomya putoria (Wiedemann, 1830) is recognized as distinct from the sub-tropical African blowfly C.chloropyga (Wiedemann, 1818) (Diptera: Calliphoridae). The biology of C.putoria in laboratory culture is described briefly with emphasis on the differences in development found in three strains of this species from Tanzania, Liberia and Brazil. All three strains were reproductively compatible and there was no evidence of F1 hybrid sterility or hybrid breakdown in subsequent generations. Larval development was significantly faster in the Brazilian strain than in the strain from Tanzania. Sexual maturity was significantly faster in adults of the Liberian and Brazilian strains compared to that found in the strain from Tanzania. This latter strain was affected by the source of protein available as adult food. These differences between strains did not appear to be due to selection in laboratory culture, but rather evidence of the evolution of physiological divergence within a species occupying different geographical regions.

Animals↗
PubMed1991

The cytosolic and glycosomal isoenzymes of glyceraldehyde-3-phosphate dehydrogenase in Trypanosoma brucei have a distant evolutionary relationship.

Trypanosoma brucei contains two isoenzymes for glyceraldehyde-3-phosphate dehydrogenase: one enzyme resides in a microbody-like organelle, the glycosome; the other is found in the cytosol. Previously we have reported the characterization of the gene for the glycosomal enzyme [Michels, P. A. M., Poliszczak, A., Osinga, K. A., Misset, O., Van Beeumen, J., Wierenga, R. K., Borst, P. & Opperdoes, F. R. (1986) EMBO J. 5, 1049-1056]. Here we describe the cloning and analysis of the gene that codes for the cytosolic isoenzyme. The gene encodes a polypeptide of 330 amino acids, with a calculated molecular mass of 35440 Da. The two isoenzymes are only 55% identical. The cytosolic glyceraldehyde-3-phosphate dehydrogenase differs from the glycosomal enzyme in the following respects: (a) its subunit molecular mass is 3.4 kDa smaller due to the absence of insertions and a small C-terminal extension which are unique to the glycosomal protein; (b) the cytosolic enzyme has a lower pI (7.9, as compared to 9.3 for the glycosomal isoenzyme), which is due to a reduction in the excess of positively charged amino acids (the calculated net charges of the polypeptides are +2 and +11, respectively). We have compared the amino acid sequences of the two T. brucei glyceraldehyde-3-phosphate dehydrogenases, with 24 available sequences of the corresponding enzyme of other organisms from various phylogenetic groups. On the basis of this comparison an evolutionary tree was constructed. This analysis strongly supports the theory that T. brucei diverged early in evolution from the main eukaryotic branch of the phylogenetic tree. Further, two separate branches for the lineages leading to Trypanosoma are inferred from the amino acid sequences, suggesting that the genes for the two glyceraldehyde-3-phosphate dehydrogenases of the trypanosome are distantly related and must have been acquired independently by the trypanosomal ancestor. The branching determined with the glycosomal enzyme precedes that found with the cytosolic enzyme. The available data do not allow us to decide which of the two genes originally belonged to the trypanosome lineage and which entered the cell later by horizontal gene transfer.

Amino Acid Sequence↗