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1.
Two previously undetected domains were identified in a variety of RNA-binding proteins, particularly RNA-modifying enzymes,
using methods for sequence profile analysis. A small domain consisting of 60–65 amino acid residues was detected in the ribosomal
protein S4, two families of pseudouridine synthases, a novel family of predicted RNA methylases, a yeast protein containing
a pseudouridine synthetase and a deaminase domain, bacterial tyrosyl-tRNA synthetases, and a number of uncharacterized, small
proteins that may be involved in translation regulation. Another novel domain, designated PUA domain, after PseudoUridine
synthase and Archaeosine transglycosylase, was detected in archaeal and eukaryotic pseudouridine synthases, archaeal archaeosine
synthases, a family of predicted ATPases that may be involved in RNA modification, a family of predicted archaeal and bacterial
rRNA methylases. Additionally, the PUA domain was detected in a family of eukaryotic proteins that also contain a domain homologous
to the translation initiation factor eIF1/SUI1; these proteins may comprise a novel type of translation factors. Unexpectedly,
the PUA domain was detected also in bacterial and yeast glutamate kinases; this is compatible with the demonstrated role of
these enzymes in the regulation of the expression of other genes. We propose that the S4 domain and the PUA domain bind RNA
molecules with complex folded structures, adding to the growing collection of nucleic acid-binding domains associated with
DNA and RNA modification enzymes. The evolution of the translation machinery components containing the S4, PUA, and SUI1 domains
must have included several events of lateral gene transfer and gene loss as well as lineage-specific domain fusions.
Received: 15 May 1998 / Accepted: 20 July 1998 相似文献
2.
Hemmi H Ishibashi J Tomie T Yamakawa M 《The Journal of biological chemistry》2003,278(25):22820-22827
Scarabaecin isolated from hemolymph of the coconut rhinoceros beetle Oryctes rhinoceros is a 36-residue polypeptide that has antifungal activity. The solution structure of scarabaecin has been determined from twodimensional 1H NMR spectroscopic data and hybrid distance geometry-simulated annealing protocol calculation. Based on 492 interproton and 10 hydrogen-bonding distance restraints and 36 dihedral angle restraints, we obtained 20 structures. The average backbone root-mean-square deviation for residues 4-35 is 0.728 +/- 0.217 A from the mean structure. The solution structure consists of a two-stranded antiparallel beta-sheet connected by a type-I beta-turn after a short helical turn. All secondary structures and a conserved disulfide bond are located in the C-terminal half of the peptide, residues 18-36. Overall folding is stabilized by a combination of a disulfide bond, seven hydrogen bonds, and numerous hydrophobic interactions. The structural motif of the C-terminal half shares a significant tertiary structural similarity with chitin-binding domains of plant and invertebrate chitin-binding proteins, even though scarabaecin has no overall sequence similarity to other peptide/polypeptides including chitin-binding proteins. The length of its primary structure, the number of disulfide bonds, and the pattern of conserved functional residues binding to chitin in scarabaecin differ from those of chitin-binding proteins in other invertebrates and plants, suggesting that scarabaecin does not share a common ancestor with them. These results are thought to provide further strong experimental evidence to the hypothesis that chitin-binding proteins of invertebrates and plants are correlated by a convergent evolution process. 相似文献
3.
4.
Molecular Phylogeny of Metazoan Intermediate Filament Proteins 总被引:7,自引:0,他引:7
Andreas Erber Dieter Riemer Marc Bovenschulte Klaus Weber 《Journal of molecular evolution》1998,47(6):751-762
We have cloned cytoplasmic intermediate filament (IF) proteins from a large number of invertebrate phyla using cDNA probes,
the monoclonal antibody IFA, peptide sequence information, and various RT-PCR procedures. Novel IF protein sequences reported
here include the urochordata and nine protostomic phyla, i.e., Annelida, Brachiopoda, Chaetognatha, Echiura, Nematomorpha,
Nemertea, Platyhelminthes, Phoronida, and Sipuncula. Taken together with the wealth of data on IF proteins of vertebrates
and the results on IF proteins of Cephalochordata, Mollusca, Annelida, and Nematoda, two IF prototypes emerge. The L-type,
which includes 35 sequences from 11 protostomic phyla, shares with the nuclear lamins the long version of the coil 1b subdomain
and, in most cases, a homology segment of some 120 residues in the carboxyterminal tail domain. The S-type, which includes
all four subfamilies (types I to IV) of vertebrate IF proteins, lacks 42 residues in the coil 1b subdomain and the carboxyterminal
lamin homology segment. Since IF proteins from all three phyla of the chordates have the 42-residue deletion, this deletion
arose in a progenitor prior to the divergence of the chordates into the urochordate, cephalochordate, and vertebrate lineages,
possibly already at the origin of the deuterostomic branch. Four phyla recently placed into the protostomia on grounds of
their 18S rDNA sequences (Brachiopoda, Nemertea, Phoronida, and Platyhelminthes) show IF proteins of the L-type and fit by
sequence identity criteria into the lophotrochozoic branch of the protostomia.
Received: 2 April 1998 / Accepted: 19 June 1998 相似文献
5.
Marcia J. Kieliszewski Allan M. Showalter Joseph F. Leykam 《The Plant journal : for cell and molecular biology》1994,5(6):849-861
Potato (Solanum tuberosum) lectin, is a chimeric chitin-binding protein comprised of a lectin domain fused to a hydroxyproline-rich glycoprotein domain. Here peptide sequence information from both domains is presented. A partial sequence of a major tryptic peptide T2: Leu-Pro-Ser-Hyp-Hyp-Hyp-Hyp-Hyp-Hyp-(His)-Hyp-Ser-Hyp-Hyp-Hyp-Hyp-Ser-Hyp-Hyp-Ser-Hyp-Hyp-Hyp-Hyp-Ser-Hyp-Hyp- was similar to the ‘P3’ type extensin major repetitive sequence: Ser-Hyp-Hyp-Hyp-Hyp-Ser-Hyp-Ser-Hyp-Hyp-Hyp-Hyp-suggesting common evolutionary origins for the extensins and the hydroxyproline-rich glycoprotein (HRGP) domain of potato lectin. Furthermore, alignment of three chymotryptic peptides from potato lectin, C1: Cys-Gly-Thr-Thr-Ser-Asp-Tyr, C2: Cys-Ser-Pro-Gly-Tyr, and C8: Thr-Gly-Glu-Cys-Cys-Ser-Ile with similar sequences from the hevein lectin family indicates that they have homologous chitin-binding domains, and hence have common evolutionary origins. Finally, all plant chitin-binding domains examined bore a remarkable sequence similarity, particularly in the spacing of Cys residues, to the disintegrins (platelet aggregation inhibitors) which occur in crotalid and viperid snake venoms. As such, sequence similarities not only identify potato lectin as a member of both the hevein and extensin families of plant proteins, but also suggest that an archetypal polypeptide module gave rise to both the plant chitin-binding domain and the reptile disintegrins. 相似文献
6.
Satoru Kanai Hiroyuki Toh Toshiya Hayano Masakazu Kikuchi 《Journal of molecular evolution》1998,47(2):200-210
Protein disulfide isomerase (PDI) is an enzyme that promotes protein folding by catalyzing disulfide bridge isomerization.
PDI and its relatives form a diverse protein family whose members are characterized by thioredoxin-like (TX) domains in the
primary structures. The family was classified into four classes by the number and the relative positions of the TX domains.
To investigate the evolution of the domain structures, we aligned the amino acid sequences of the TX domains, and the molecular
phylogeny was examined by the NJ and ML methods. We found that all of the current members of the PDI family have evolved from
an ancestral enzyme, which has two TX domains in the primary structure. The diverse domain structures of the members have
been generated through domain duplications and deletions. 相似文献
7.
Fungi have evolved a unique α-aminoadipate pathway for lysine biosynthesis. The fungal-specific enzyme homoaconitate hydratase
from this pathway is moderately similar to the aconitase-family proteins from a diverse array of taxonomic groups, which have
varying modes of obtaining lysine. We have used the similarity of homoaconitate hydratase to isopropylmalate isomerase (serving
in leucine biosynthesis), aconitase (from the tricarboxylic acid cycle), and iron-responsive element binding proteins (cytosolic
aconitase) from fungi and other eukaryotes, eubacteria, and archaea to evaluate possible evolutionary scenarios for the origin
of this pathway. Refined sequence alignments show that aconitase active site residues are highly conserved in each of the
enzymes, and intervening sequence sites are quite dissimilar. This pattern suggests strong purifying selection has acted to
preserve the aconitase active site residues for a common catalytic mechanism; numerous other substitutions occur due to adaptive
evolution or simply lack of functional constraint. We hypothesize that the similarities are the remnants of an ancestral gene
duplication, which may not have occurred within the fungal lineage. Maximum likelihood, neighbor joining, and maximum parsimony
phylogenetic comparisons show that the α-aminoadipate pathway enzyme is an outgroup to all aconitase family proteins for which
sequence is currently available.
Received: 7 October 1997 相似文献
8.
Evolutionary Comparisons of RecA-Like Proteins Across All Major Kingdoms of Living Organisms 总被引:17,自引:0,他引:17
Volker Brendel Luciano Brocchieri Steven J. Sandler Alvin J. Clark Samuel Karlin 《Journal of molecular evolution》1997,44(5):528-541
Protein sequences with similarities to Escherichia coli RecA were compared across the major kingdoms of eubacteria, archaebacteria, and eukaryotes. The archaeal sequences branch
monophyletically and are most closely related to the eukaryotic paralogous Rad51 and Dmc1 groups. A multiple alignment of
the sequences suggests a modular structure of RecA-like proteins consisting of distinct segments, some of which are conserved
only within subgroups of sequences. The eukaryotic and archaeal sequences share an N-terminal domain which may play a role
in interactions with other factors and nucleic acids. Several positions in the alignment blocks are highly conserved within
the eubacteria as one group and within the eukaryotes and archaebacteria as a second group, but compared between the groups
these positions display nonconservative amino acid substitutions. Conservation within the RecA-like core domain identifies
possible key residues involved in ATP-induced conformational changes. We propose that RecA-like proteins derive evolutionarily
from an assortment of independent domains and that the functional homologs of RecA in noneubacteria comprise an array of RecA-like
proteins acting in series or cooperatively.
Received: 25 October 1996 / Accepted: 31 December 1996 相似文献
9.
Gerhard Schenk Roy Layfield Judith M. Candy Ronald G. Duggleby Peter F. Nixon 《Journal of molecular evolution》1997,44(5):552-572
Members of the transketolase group of thiamine-diphosphate-dependent enzymes from 17 different organisms including mammals,
yeast, bacteria, and plants have been used for phylogenetic reconstruction. Alignment of the amino acid and DNA sequences
for 21 transketolase enzymes and one putative transketolase reveals a number of highly conserved regions and invariant residues
that are of predicted importance for enzyme activity, based on the crystal structure of yeast transketolase. One particular
sequence of 36 residues has some similarities to the nucleotide-binding motif and we designate it as the transketolase motif.
We report further evidence that the recP protein from Streptococcus pneumoniae might be a transketolase and we list a number of invariant residues which might be involved in substrate binding. Phylogenies
derived from the nucleotide and the amino acid sequences by various methods show a conventional clustering for mammalian,
plant, and gram-negative bacterial transketolases. The branching order of the gram-positive bacteria could not be inferred
reliably. The formaldehyde transketolase (sometimes known as dihydroxyacetone synthase) of the yeast Hansenula polymorpha appears to be orthologous to the mammalian enzymes but paralogous to the other yeast transketolases. The occurrence of more
than one transketolase gene in some organisms is consistent with several gene duplications. The high degree of similarity
in functionally important residues and the fact that the same kinetic mechanism is applicable to all characterized transketolase
enzymes is consistent with the proposition that they are all derived from one common ancestral gene. Transketolase appears
to be an ancient enzyme that has evolved slowly and might serve as a model for a molecular clock, at least within the mammalian
clade.
Received: 13 September 1995 / Accepted: 14 November 1996 相似文献
10.
Benoit Cousineau Fabrice Leclerc Robert Cedergren 《Journal of molecular evolution》1997,45(6):661-670
Sequence similarity has given rise to the proposal that IF-2, EF-G, and EF-Tu are related through a common ancestor. We evaluate
this proposition and whether the relationship can be extended to other factors of protein synthesis. Analysis of amino acid
sequence similarity gives statistical support for an evolutionary affiliation among IF-1, IF-2, IF-3, EF-Tu, EF-Ts, and EF-G
and suggests further that this association is a result of gene duplication/fusion events. In support of this mechanism, the
three-dimensional structures of IF-3, EF-Tu, and EF-G display a predictable domain structure and overall conformational similarity.
The model that we propose consists of three consecutives duplication/fusion events which would have taken place before the
divergence of the three superkingdoms: eubacteria, archaea, and eukaryotes. The root of this protein superfamily tree would
be an ancestor of the modern IF-1 gene sequence. The repeated fundamental motif of this protein superfamily is a small RNA
binding domain composed of two α-helices packed along side of an antiparallel β-sheet.
Received: 17 October 1996 / Accepted: 10 June 1997 相似文献
11.
One of the most remarkable biochemical differences between the members of two domains Archaea and Bacteria is the stereochemistry
of the glycerophosphate backbone of phospholipids, which are exclusively opposite. The enzyme responsible to the formation
of Archaea-specific glycerophosphate was found to be NAD(P)-linked sn-glycerol-1-phosphate (G-1-P) dehydrogenase and it was first purified from Methanobacterium thermoautotrophicum cells and its gene was cloned. This structure gene named egsA (enantiomeric glycerophosphate synthase) consisted of 1,041 bp and coded the enzyme with 347 amino acid residues. The amino
acid sequence deduced from the base sequence of the cloned gene (egsA) did not share any sequence similarity except for NAD-binding region with that of NAD(P)-linked sn-glycerol-3-phosphate (G-3-P) dehydrogenase of Escherichia coli which catalyzes the formation of G-3-P backbone of bacterial phospholipids, while the deduced protein sequence of the enzyme
revealed some similarity with bacterial glycerol dehydrogenases. Because G-1-P dehydrogenase and G-3-P dehydrogenase would
originate from different ancestor enzymes and it would be almost impossible to interchange stereospecificity of the enzymes,
it seems likely that the stereostructure of membrane phospholipids of a cell must be maintained from the time of birth of
the first cell. We propose here the hypothesis that Archaea and Bacteria were differentiated by the occurrence of cells enclosed
by membranes of phospholipids with G-1-P and G-3-P as a backbone, respectively.
Received: 24 March 1997 / Accepted: 21 May 1997 相似文献
12.
Multidrug resistance to anti-cancer drugs is a major medical problem. Resistance is manifested largely by the product of
the human MDR1 gene, P-glycoprotein, an ABC transporter that is an integral membrane protein of 1280 amino acids arranged into two homologous
halves, each comprising 6 putative transmembrane α-helices and an ATP binding domain. Despite the plethora of data from site-directed,
scanning and domain replacement mutagenesis, epitope mapping and photoaffinity labeling, a clear structural model for P-glycoprotein
remains largely elusive. In this report, we propose a new model for P-glycoprotein that is supported by the vast body of previous
data. The model comprises 2 membrane-embedded 16-strand β-barrels, attached by short loops to two 6-helix bundles beneath
each barrel. Each ATP binding domain contributes 2 β-strands and 1 α-helix to the structure. This model, together with an
analysis of the amino acid sequence alignment of P-glycoprotein isoforms, is used to delineate drug binding and translocation
sites. We show that the locations of these sites are consistent with mutational, kinetic and labeling data.
Received: 18 February 1998/Revised: 2 September 1998 相似文献
13.
Patrick J. Babin Jan Bogerd Frank P. Kooiman Wil J. A. Van Marrewijk Dick J. Van der Horst 《Journal of molecular evolution》1999,49(1):150-160
Large lipid transfer proteins (LLTP) are nonexchangeable apolipoproteins and intracellular lipid-exchange proteins involved
in the assembly, secretion, and metabolism of lipoproteins. We have identified contiguous conserved sequence motifs in alignments
of insect apolipophorin II/I precursor (apoLp-II/I), human apolipoprotein B (apoB), invertebrate and vertebrate vitellogenins
(VTG), and the large subunit of mammalian microsomal triglyceride transfer protein (MTP). Conserved motifs present in the
N-terminal part of nonexchangeable apolipoproteins encompass almost completely the large subunit of MTP, suggesting a derivation
from a common ancestral functional unit, termed large lipid transfer (LLT) module. Divergence of LLTP from a common ancestor
is supported by (1) the statistical significance of the combined match scores obtained after motif-based database searches,
(2) the presence of several identical amino acid residues in all LLTP sequences currently available, (3) the conservation
of hydrophobic clusters in an α-helical domain, (4) the phylogenetic analysis of the conserved sequences related to the von
Willebrand factor D (VWD) module identified in nonexchangeable apolipoproteins, and (5) the presence of four and one ancestral
exon boundaries in the LLT and VWD modules, respectively. Our data indicate that the genes coding for apoLp-II/I, apoB, VTG,
and the MTP large subunit are members of the same multigene superfamily. LLTP have emerged from an ancestral molecule designed
to ensure a pivotal event in the intracellular and extracellular transfer of lipids and liposoluble substances.
Received: 8 June 1998 / Accepted: 15 February 1999 相似文献
14.
Actin is a highly conserved protein although many isoforms exist. In vertebrates and insects the different actin isoforms
can be grouped by their amino acid sequence and tissue-specific gene expression into muscle and nonmuscle actins, suggesting
that the different actins may have a functional significance. We ask here whether atomic models for G- and F-actins may help
to explain this functional diversity. Using a molecular graphics program we have mapped the few amino acids that differ between
isoactins. A small number of residues specific for muscle actins are buried in internal positions and some present a remarkable
organization. Within the molecule, the replacements observed between muscle and nonmuscle actins are often accompanied by
compensatory changes. The others are dispersed on the protein surface, except for a cluster located at the N-terminus which
protrudes outward. Only a few of these residues specific for muscle actins are present in known ligand binding sites except
the N-terminus, which has a sequence specific for each isoactin and is directly implicated in the binding to myosin. When
we simulated the replacements of side chains of residues specific for muscle actins to those specific for nonmuscle actins,
the N-terminus appears to be less compact and more flexible in nonmuscle actins. This would represent the first conformational
grounds for proposing that muscle and nonmuscle actins may be functionally distinguishable. The rest of the molecule is very
similar or identical in all the actins, except for a possible higher internal flexibility in muscle actins. We propose that
muscle actin genes have evolved from genes of nonmuscle actins by substitutions leading to some conformational changes in
the protruding N-terminus and the internal dynamics of the main body of the protein.
Received: 15 March 1996 / Accepted: 14 July 1996 相似文献
15.
Summary
Bumetanide-sensitive Na-K-Cl cotransporters and thiazide-sensitive Na-Cl cotransporters comprise a family of integral membrane
transport proteins, the Na-K-Cl cotransporter (NKCC) family. Each of the members of this family is over 1,000 amino acids
in length. We have multiply aligned the ten currently sequenced members of this family from human, rabbit, rodent, shark,
flounder, moth, worm and yeast sources. Phylogenetic analyses suggest the presence of at least six isoforms of these full
length proteins in eukaryotes. Average hydropathy and average similarity plots have been derived revealing that each of these
proteins possesses a central, well conserved, hydrophobic domain of almost invariant length, possibly consisting of twelve
transmembrane α-helical spanners, an N-terminal, poorly conserved, hydrophilic domain of variable length, and a C-terminal,
moderately conserved, hydrophilic domain of moderately constant length. A functionally uncharacterized homologue of this family
occurs in the cyanobacterium Synechococcus sp. Limited sequence similarity of these proteins with members of a family of basic amino acid transporters suggests that the
NKCC family may be distantly related to the previously characterized, ubiquitous, amino acid-polyamine-choline (APC) family
of facilitators. These observations suggest that the NKCC family is an old family that has its roots in the prokaryotic kingdom.
Received: 27 July 1995/Revised: 8 November 1995 相似文献
16.
Francine Hamel Rodolphe Boivin Colette Tremblay Guy Bellemare 《Journal of molecular evolution》1997,44(6):614-624
The analysis of nuclear-encoded chitinase sequences from various angiosperms has allowed the categorization of the chitinases
into discrete classes. Nucleotide sequences of their catalytic domains were compared in this study to investigate the evolutionary
relationships between chitinase classes. The functionally distinct class III chitinases appear to be more closely related
to fungal enzymes involved in morphogenesis than to other plant chitinases. The ordering of other plant chitinases into additional
classes mainly relied on the presence of auxiliary domains—namely, a chitin-binding domain and a carboxy-terminal extension—flanking
the main catalytic domain. The results of our phylogenetic analyses showed that classes I and IV form discrete and well-supported
monophyletic groups derived from a common ancestral sequence that predates the divergence of dicots and monocots. In contrast,
other sequences included in classes I* and II, lacking one or both types of auxiliary domains, were nested within class I
sequences, indicating that they have a polyphyletic origin. According to phylogenetic analyses and the calculation of evolutionary
rates, these chitinases probably arose from different class I lineages by relatively recent deletion events. The occurrence
of such evolutionary trends in cultivated plants and their potential involvement in host–pathogen interactions are discussed.
Received: 5 July 1996 / Accepted: 9 January 1997 相似文献
17.
The amino acid sequences of 22 α-amylases from family 13 of glycosyl hydrolases were analyzed with the aim of revealing the
evolutionary relationships between the archaeal α-amylases and their eubacterial and eukaryotic counterparts. Two evolutionary
distance trees were constructed: (i) the first one based on the alignment of extracted best-conserved sequence regions (58
residues) comprising β2, β3, β4, β5, β7, and β8 strand segments of the catalytic (α/β)8-barrel and a short conserved stretch in domain B protruding out of the barrel in the β3 →α3 loop, and (ii) the second one
based on the alignment of the substantial continuous part of the (α/β)8-barrel involving the entire domain B (consensus length: 386 residues). With regard to archaeal α-amylases, both trees compared
brought, in fact, the same results; i.e., all family 13 α-amylases from domain Archaea were clustered with barley pI isozymes,
which represent all plant α-amylases. The enzymes from Bacillus licheniformis and Escherichia coli, representing liquefying and cytoplasmic α-amylases, respectively, seem to be the further closest relatives to archaeal α-amylases.
This evolutionary relatedness clearly reflects the discussed similarities in the amino acid sequences of these α-amylases,
especially in the best-conserved sequence regions. Since the results for α-amylases belonging to all three domains (Eucarya,
Eubacteria, Archaea) offered by both evolutionary trees are very similar, it is proposed that the investigated conserved sequence
regions may indeed constitute the ``sequence fingerprints' of a given α-amylase.
Received: 3 June 1998 / Accepted: 20 August 1998 相似文献
18.
Glutamine synthetase type I (GSI) genes have previously been described only in prokaryotes except that the fungus Emericella nidulans contains a gene (fluG) which encodes a protein with a large N-terminal domain linked to a C-terminal GSI-like domain. Eukaryotes generally contain
the type II (GSII) genes which have been shown to occur also in some prokaryotes. The question of whether GSI and GSII genes
are orthologues or paralogues remains a point of controversy. In this article we show that GSI-like genes are widespread in
higher plants and have characterized one of the genes from the legume Medicago truncatula. This gene is part of a small gene family and is expressed in many organs of the plant. It encodes a protein similar in size
and with between 36 and 46% amino acid sequence similarity to prokaryotic GS proteins used in the analyses, whereas it is
larger and with less than 25% similarity to GSII proteins, including those from the same plant species. Phylogenetic analyses
suggest that this protein is most similar to putative proteins encoded by expressed sequence tags of other higher plant species
(including dicots and a monocot) and forms a cluster with FluG as the most divergent of the GSI sequences. The discovery of
GSI-like genes in higher plants supports the paralogous evolution of GSI and GSII genes, which has implications for the use
of GS in molecular studies on evolution.
Received: 4 May 1999 / Accepted: 17 September 1999 相似文献
19.
The mammalian immune system has cytotoxic mechanisms, both cellular and humoral, that destroy the membrane integrity of target
cells. The main effector molecules of these cytolytic mechanisms—perforin, used by killer lymphocytes, and the membrane attack
complex (MAC) components of the complement system—share a unique module called the MAC/perforin module. Until now, both immunological
cytotoxicity and the MAC/perforin module have been reported only in jawed vertebrates. Here, we report the identification
of a protein containing the MAC/perforin module from the invertebrate cephalochordate, amphioxus (Branchiostoma belcheri), using expressed sequence tag (EST) analysis of the notochord. The deduced amino acid sequence of this molecule is most
similar to the primary structure of human complement component C6 and is designated AmphiC6. AmphiC6 shares a unique modular
structure, including the MAC/perforin module, with human C6 and other MAC components. Another EST clone predicts the presence
of a thioester-containing protein with the closest structural similarity to vertebrate C3 (therefore designated AmphiC3).
AmphiC3 retains most of the functionally important residues of vertebrate C3 and is shown by phylogenetic analysis to be derived
directly from the common ancestor of vertebrate C3, C4, and C5. Only opsonic activity has been assigned to the invertebrate
complement system until now. Therefore, this is the first molecular evidence for complement-mediated immunological cytotoxicity
in invertebrates.
Received: 24 August 2001 / Accepted: 12 November 2001 相似文献
20.
Microbial Relatives of Seed Storage Proteins: Conservation of Motifs in a Functionally Diverse Superfamily of Enzymes 总被引:1,自引:0,他引:1
Plant storage proteins comprise a major part of the human diet. Sequence analysis has revealed that these proteins probably
share a common ancestor with a fungal oxalate decarboxylase and/or related bacterial genes. Additionally, all these proteins
share a central core sequence with several other functionally diverse enzymes and binding proteins, many of which are associated
with synthesis of the extracellular matrix during sporulation/encystment. A possible prokaryotic relative of this sequence
is a bacterial protein (SASP) known to bind to DNA and thereby protect spores from extreme environmental conditions. This
ability to maintain cell viability during periods of dehydration in spores and seeds may relate to absolute conservation of
residues involved in structure determination.
Received: 25 April 1997 / Accepted: 29 July 1997 相似文献