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PubMed1991

Nucleotide sequence of a DNA region comprising the gene for elongation factor 1 alpha (EF-1 alpha) from the ultrathermophilic archaeote Pyrococcus woesei: phylogenetic implications.

The gene encoding elongation factor 1 alpha (EF-1 alpha, 1290 bp) of the ultrathermophilic, sulfur-reducing archaeote Pyrococcus woesei was localized within a Bg/II fragment of chromosomal DNA. Sequence analysis showed that the EF-1 alpha gene is the upstream unit of a three-gene cluster comprising the genes for ribosomal protein S10 (306 bp) and transfer RNAser (GGA). The three genes follow each other immediately in the order EF-1 alpha.S10.tRNA(ser) after a putative promoter located 55 bp upstream of the EF-1 alpha gene. Alignment of the derived EF-1 alpha sequence with the corresponding sequences from Eukarya, Bacteria/organelles, and with available archaeal sequences (Sulfolobus, Thermococcus, Methanococcus, Halobacterium) showed that Pyrococcus EF-1 alpha is highly homologous (89% identity) to Thermococcus celer EF-1 alpha, both being strikingly more similar to eukaryotic EF-1 alpha than to bacterial EF-Tu. Unrooted dendrograms computed from aligned sequences by distance matrix and DNA parsimony methods, including evolutionary parsimony, showed the Archaea to be a monophyletic-holophyletic cluster closer to Eukarya than to Bacteria. Both distance matrix and DNA parsimony--although not evolutionary parsimony--support the partition of the known archaeal lineages between the kingdoms Crenarchaeota and Euryarchaeota, and the affiliation of the Pyrococcus-Thermococcus lineage to the Euryarchaeota, of which it is the most primitive offspring. A closer relation of Pyrococcus to Euryarchaeota than to Crenarchaeota was also inferred from sequence analysis of S10 ribosomal proteins.

Amino Acid Sequence↗
PubMed1991

Phylogenetic depth of Thermotoga maritima inferred from analysis of the fus gene: amino acid sequence of elongation factor G and organization of the Thermotoga str operon.

The gene (fus) coding for elongation factor G (EF-G) of the extremely thermophilic eubacterium Thermotoga maritima was identified and sequenced. The EF-G coding sequence (2046 bp) was found to lie in an operon-like structure between the ribosomal protein S7 gene (rpsG) and the elongation factor Tu (EF-Tu) gene (tuf). The rpsG, fus, and tuf genes follow each other immediately in that order, which corresponds to the order of the homologous genes in the str operon of Escherichia coli. The derived amino acid sequence of the EF-G protein (682 residues) was aligned with the homologous sequences of other eubacteria, eukaryotes (hamster), and archaebacteria (Methanococcus vannielii). Unrooted phylogenetic dendrograms, obtained both from the amino acid and the nucleotide sequence alignments, using a variety of methods, lend further support to the notion that the (present) root of the (eu)bacterial tree lies between Thermotoga and the other bacterial lineages.

Amino Acid Sequence↗
PubMed1997

Conserved gene clusters in bacterial genomes provide further support for the primacy of RNA.

Five complete bacterial genome sequences have been released to the scientific community. These include four (eu)Bacteria, Haemophilus influenzae, Mycoplasma genitalium, M. pneumoniae, and Synechocystis PCC 6803, as well as one Archaeon, Methanococcus jannaschii. Features of organization shared by these genomes are likely to have arisen very early in the history of the bacteria and thus can be expected to provide further insight into the nature of early ancestors. Results of a genome comparison of these five organisms confirm earlier observations that gene order is remarkably unpreserved. There are, nevertheless, at least 16 clusters of two or more genes whose order remains the same among the four (eu)Bacteria and these are presumed to reflect conserved elements of coordinated gene expression that require gene proximity. Eight of these gene orders are essentially conserved in the Archaea as well. Many of these clusters are known to be regulated by RNA-level mechanisms in Escherichia coli, which supports the earlier suggestion that this type of regulation of gene expression may have arisen very early. We conclude that although the last common ancestor may have had a DNA genome, it likely was preceded by progenotes with an RNA genome.

Archaea↗
PubMed1998

The prokaryote-to-eukaryote transition reflected in the evolution of the V/F/A-ATPase catalytic and proteolipid subunits.

Changes in the primary and quarternary structure of vacuolar and archaeal type ATPases that accompany the prokaryote-to-eukaryote transition are analyzed. The gene encoding the vacuolar-type proteolipid of the V-ATPase from Giardia lamblia is reported. Giardia has a typical vacuolar ATPase as observed from the common motifs shared between its proteolipid subunit and other eukaryotic vacuolar ATPases, suggesting that the former enzyme works as a hydrolase in this primitive eukaryote. The phylogenetic analyses of the V-ATPase catalytic subunit and the front and back halves of the proteolipid subunit placed Giardia as the deepest branch within the eukaryotes. Our phylogenetic analysis indicated that at least two independent duplication and fusion events gave rise to the larger proteolipid type found in eukaryotes and in Methanococcus. The spatial distribution of the conserved residues among the vacuolar-type proteolipids suggest a zipper-type interaction among the transmembrane helices and surrounding subunits of the V-ATPase complex. Important residues involved in the function of the F-ATP synthase proteolipid have been replaced during evolution in the V-proteolipid, but in some cases retained in the archaeal A-ATPase. Their possible implication in the evolution of V/F/A-ATPases is discussed.

Amino Acid Sequence↗
PubMed1999

Archaeabacterial seryl-tRNA synthetases: adaptation to extreme environments and evolutionary analysis.

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.

Adaptation, Physiological↗
PubMed1997

Function of coenzyme F420-dependent NADP reductase in methanogenic archaea containing an NADP-dependent alcohol dehydrogenase.

Methanogenic archaea growing on ethanol or isopropanol as the electron donor for CO2 reduction to CH4 contain either an NADP-dependent or a coenzyme F420-dependent alcohol dehydrogenase. We report here that in both groups of methanogens, the N5, N10-methylenetetrahydromethanopterin dehydrogenase and the N5, N10-methylenetetrahydromethanopterin reductase, two enzymes involved in CO2 reduction to CH4, are specific for F420. This raised the question how F420H2 is regenerated in the methanogens with an NADP-dependent alcohol dehydrogenase. We found that these organisms contain catabolic activities of an enzyme catalyzing the reduction of F420 with NADPH. The F420-dependent NADP reductase from Methanogenium organophilum was purified and characterized. The N-terminal amino acid sequence showed 42% sequence identity to a putative gene product in Methanococcus jannaschii, the total genome of which has recently been sequenced.

Alcohol Oxidoreductases↗
PubMed1998

A 71-kDa protein from Halobacterium salinarium belongs to a ubiquitous P-loop ATPase superfamily with head-rod-tail structure.

The nucleotide sequence of a genomic fragment from Halobacterium salinarium containing an open reading frame encoding a protein with a calculated molecular mass of 71 kDa was determined. Database searches revealed that this protein, Hp71, has similarities to eukaryotic cytoskeletal proteins. Heterologous production of Hp71 in Escherichia coli allowed the isolation of anti-Hp71 antibodies. The antibodies were used (1) to verify the production of Hp71 in H. salinarium and (2) to determine its cytoplasmic localization by immune electron microscopy. Homologous overproduction of Hp71 in H. salinarium and heterologous production in Haloferax volcanii resulted in modifications of cell morphology from rods to extended rods, and from pleiomorphic cells to rods, respectively. Structure prediction methods indicated that Hp71 has a head-rod-tail configuration, including an N-terminal domain with a nucleotide binding motif (P-loop), and an extended discontinuous coiled-coil domain of 330 amino acids. To identify related proteins, the complete genomes of Haemophilus influenzae, Mycoplasma genitalium, and Methanococcus jannaschii were searched for deduced proteins with extended coiled-coil domains. Only one or two proteins were found for each organism, showing that Hp71 is one of only a few prokaryotic intracellular proteins with extended coiled-coil domains. The phenotype upon overproduction and the similarity of Hp71 to the SMC superfamily of P-loop head-rod-tail proteins (named after SMC1, which is involved in the "stability of minichromosomes" in yeast) indicate that Hp71 might be involved in cytoskeleton formation and/or chromosome partitioning in H. salinarium.

Adenosine Triphosphatases↗
PubMed2001

Correlation between Shine--Dalgarno sequence conservation and codon usage of bacterial genes.

In this study, we analyzed the correlation between codon usage bias and Shine--Dalgarno (SD) sequence conservation, using complete genome sequences of nine prokaryotes. For codon usage bias, we adopted the codon adaptation index (CAI), which is based on the codon usage preference of genes encoding ribosomal proteins, elongation factors, heat shock proteins, outer membrane proteins, and RNA polymerase subunit proteins. To compute SD sequence conservation, we used SD motif sequences predicted by Tompa and systematically aligned them with 5'UTR sequences. We found that there exists a clear correlation between the CAI values and SD sequence conservation in the genomes of Escherichia coli, Bacillus subtilis, Haemophilus influenzae, Archaeoglobus fulgidus, Methanobacterium thermoautotrophicum, and Methanococcus jannaschii, and no relationship is found in M. genitalium, M. pneumoniae, and Synechocystis. That is, genes with higher CAI values tend to have more conserved SD sequences than do genes with lower CAI values in these organisms. Some organisms, such as M. thermoautotrophicum, do not clearly show the correlation. The biological significance of these results is discussed in the context of the translation initiation process and translation efficiency.

Base Sequence↗
PubMed2002

Mechanosensitive channels of bacteria and archaea share a common ancestral origin.

The ubiquity of mechanosensitive (MS) ion channels set off a search for their functional homologues in archaea, the third domain of life. A new MS channel was identified in the archaeon Methanococcus jannaschii by using the TM1 transmembrane domain of the bacterial MS channel of large conductance, MscL, as a genetic probe to search the archaeal genomic database for MS channel homologues. The hypothetical protein MJ0170 (MscMJ) was found to harbor two MscL-like TM1 structural motifs and showed a high degree of se quence and secondary structure conservation with MscS (YggB) homologues. The alignment of sequences of MscL, MscS and MscMJ homologues further revealed that bacterial and archaeal channels form a phylogenetic tree composed of three main branches and share a common ancestral origin. This suggests the evolution of prokaryotic MS channels via gene duplication of a MscL-like progenitor gene followed by divergence, fur ther indicating that the common ancestor of the prokaryotic MS channels most likely resembled MscL. When expressed in E. coli and functionally examined by the patch clamp, the MscMJ protein behaved as a MS channel with a conductance of 270 pS in 200 mM KCl and a cation selectivity (PK/PC]) of approximately 6. The structural and functional homologue of MscMJ, MscMJLR, was identified as a second type of MS channel in M. jannaschii. The channel has a conductance of approximately 2 nS, rectifies with voltage and shares cation selectivity with MscMJ. The stoichiometry of both types of MS channels revealed that the free energy of activation, deltaG0 approximately 7kT, obtained for MscMJ matches the one calculated for MscS, deltaG0 approximately 5kT, whereas the free energy of activation approximately deltaG0 approximately 18kT of MscMJLR resembles more the deltaG0 = 14-19kT reported for MscL. The presence of two types of MS channels discovered in the cell envelope of M. jannaschii indicates that multiplicity of MS channels in prokaryotes is a necessary element for their survival in the habitats frequently challenged by sudden changes in osmolarity. Further functional and phylogenetic study of MS channels from all three domains of the universal phylogenetic tree may help to understand the evolution and common biophysical principles that govern mechanosensory transduction.

Amino Acid Sequence↗
PubMed1997

Heat-shock response in Methanosarcina mazei S-6.

The dnaK locus of Methanosarcina mazei S-6, a mesophilic organism of the phylogenetic domain Archaea, contains the heat-shock genes 5'-grpE-dnaK-dnaJ-3'. Parameters known to affect the response of these genes in organisms of the other two domains, Bacteria and Eucarya, were tested to determine their effects on the archaeal homologs. The mRNA from the three genes increased after heat shock more in lamina than in single cells (these S-6 morphologic stages can be grown in the same substrate). Single cells in early stationary phase showed the highest levels of dnaK mRNA after heat shock, as compared with cells in exponential, or in late stationary, phase. The dnaK mRNA always had the size of a monocistronic transcript. dnaK was also found in the thermophileMethanosarcina thermophila TM-1, and its response to heat shock showed distinctive characteristics. However, dnaK was not revealed in other archaea: three hyperthermophiles (Methanothermus fervidus,Methanococcus jannaschii, and Sulfolobus sp.), and one mesophilic methanogen (Methanospirillum hungateii).

Archaea↗
PubMed2001

Conservation of the basic pattern of cellular amino acid composition of archaeobacteria during biological evolution and the putative amino acid composition of primitive life forms.

Previous studies showed that the cellular amino acid composition obtained by amino acid analysis of whole cells, differs such as eubacteria, protozoa, fungi and mammalian cells. These results suggest that the difference in the cellular amino acid composition reflects biological changes as the result of evolution. However, the basic pattern of cellular amino acid composition was relatively constant in all organisms examined. In the present study, we examined archaeobacteria, because they are considered important in understanding the relationship between biological evolution and cellular amino acid composition. The cellular amino acid compositions of Archaeoglobus fulgidus, Pyrococcus horikoshii, Methanobacterium thermoautotrophicum and Methanococcus jannaschii differed slightly from each other, but were similar to those determined from codon usage data, based on the complete genomes. Thus, the cellular amino acid composition reflects biological evolution. We suggest that primitive forms of life appearing on earth at the end of prebiotic evolution had a similar-cellular amino acid composition.

Amino Acids↗
PubMed2002

Holliday junction-resolving enzymes from eight hyperthermophilic archaea differ in reactions with cruciform DNA.

Holliday junction-resolving enzymes have been identified in a broad variety of organisms and tissues. In this study, six new Holliday junction-cleaving enzymes (Hjcs) were obtained from hyperthermophilic crenarchaeal and euryarchaeal species, including Pyrococcus horikoshii, Pyrococcus abyssi, Methanococcus jannaschii, Methanobacterium thermautotrophicum, Archaeoglobus fulgidus, and Aeropyrum pernix. The genes were cloned and overexpressed in Escherichia coli, and the respective proteins were purified from crude extracts to homogeneity. For an initial characterization of the enzymatic activities, synthetic heat-stable fixed and mobile cruciform DNA substrates were used at 75 degrees C. The Hjcs from Pyrococcus furiosus, Sulfolobus solfataricus, and the archaeal virus SIRV2 were included in the study for comparison. Despite their sequence homology, the enzymes showed marked differences in their reactions with individual cruciform DNAs. While the fixed cruciform structure was cleaved by all enzymes at only one major position, the mobile cruciform structure displayed different cleavage patterns for individual Hjcs, each with several cleavage positions. Furthermore, a strong bias for cleavage of one direction across the junction was observed with the fixed cruciform DNA for all enzymes. In contrast, the mobile cruciform DNA displayed different preferences, depending on the enzyme used.

Amino Acid Sequence↗
PubMed2003

ADP-dependent 6-phosphofructokinase, an extremely thermophilic, non-allosteric enzyme from the hyperthermophilic, sulfate-reducing archaeon Archaeoglobus fulgidus strain 7324.

The hyperthermophilic, sulfate-reducing archaeon Archaeoglobus fulgidus strain 7324 has been shown to degrade starch via glucose using a modified Embden-Meyerhof pathway. In this pathway phosphorylation of fructose-6-phosphate to fructose-1,6 bisphosphate is catalyzed by an ADP-dependent 6-phosphofructokinase (ADP-PFK), which was purified 1,800-fold to homogeneity. The enzyme is composed of 50 kDa subunits and is eluted from gel filtration as both a homotetramer and a homodimer. It had a temperature optimum at 85 degrees C and showed significant thermostability up to 95 degrees C. Kinetic constants were determined for both reaction directions at pH 6.6 and 80 degrees C. Rate dependence for all substrates followed Michaelis Menten kinetics. The apparent Km for ADP and fructose-6-phosphate (forward reaction) was 0.6 mM and 2.2 mM, respectively; the apparent Vmax was 1,200 U/mg. ADP-PFK catalyzed in vitro the reverse reaction, with apparent Km for fructose-1,6-bisophosphate and AMP of 5.7 and 1.4 mM, respectively, and a Vmax value of 85 U/mg. The enzyme did not use ATP, PPi, or acetyl phosphate as phosphoryl donor and was highly specific for fructose-6-phosphate as substrate. The A. fulgidus ADP-PFK did not phosphorylate glucose and thus differs from the bifunctional ADP-PFK/GLK from Methanococcus jannaschii. Divalent cations were required for catalytic activity; Mg2+, which was most effective, could be partially replaced by Mn2+, Ni2+, and Co2+. Enzyme activity was not allosterically regulated by classical effectors of bacterial and eukaryal ATP-PFKs, such as ADP, AMP, phosphoenolpyruvate, or citrate. N-terminal amino acid sequence showed high similarity to known ADP-PFKs. In the genome of Archaeoglobus fulgidus strain VC 16, which is closely related to strain 7324, no homologous gene for ADP-PFK could be identified.

Amino Acid Sequence↗
PubMed2006

Composition of archaeal, bacterial, and eukaryal RuBisCO genotypes in three Western Pacific arc hydrothermal vent systems.

We studied the diversity of all forms of the RuBisCO large subunit-encoding gene cbbL in three RuBisCO uncharacterized hydrothermal vent communities. This diversity included the archaeal cbbL and the forms IC and ID, which have not previously been studied in the deep-sea environment, in addition to the forms IA, IB and II. Vent plume sites were Fryer and Pika in the Mariana arc and the Suiyo Seamount, Izu-Bonin, Japan. The cbbL forms were PCR amplified from plume bulk microbial DNA and then cloned and sequenced. Archaeal cbbL was detected in the Mariana samples only. Both forms IA and II were amplified from all samples, while the form IC was amplified only from the Pika and Suiyo samples. Only the Suiyo sample showed amplification of the form ID. The form IB was not recorded in any sample. Based on rarefaction analysis, nucleotide diversity and average pairwise difference, the archaeal cbbL was the most diverse form in Mariana samples, while the bacterial form IA was the most diverse form in the Suiyo sample. Also, the Pika sample harbored the highest diversity of cbbL phylogenetic lineages. Based on pairwise reciprocal library comparisons, the Fryer and Pika archaeal cbbL libraries showed the most significant difference, while Pika and Suiyo showed the highest similarity for forms IA and II libraries. This suggested that the Fryer supported the most divergent sequences. All archaeal cbbL sequences formed unique phylogenetic lineages within the branches of anaerobic thermophilic archaea of the genera Pyrococcus, Archaeoglobus, and Methanococcus. The other cbbL forms formed novel phylogenetic clusters distinct from any recorded previously in other deep-sea habitats. This is the first evidence for the diversity of archaeal cbbL in environmental samples.

Archaea↗
PubMed1998

Overproduction and one-step purification of the N5,N10-methenyltetrahydromethanopterin cyclohydrolase (Mch) from the hyperthermophilic Methanopyrus kandleri.

N5,N10-Methenyltetrahydromethanopterin cyclohydrolase (Mch) is an enzyme involved in methanogenesis from CO2 and H2 which represents the energy metabolism of Methanopyrus kandleri, a methanogenic Archaeon growing at a temperature optimum of 98 degrees C. The gene mch from M. kandleri was cloned, sequenced, and expressed in Escherichia coli. The overproduced enzyme could be purified in yields above 90% in one step by chromatography on phenyl Sepharose in 80% ammonium sulfate. From 3.5 g cells (250 mg protein), approximately 18 mg cyclohydrolase was obtained. The purified enzyme showed essentially the same catalytic properties as the enzyme purified from M. kandleri cells. The primary structure and properties of the cyclohydrolase are compared with those of the enzyme from Methanococcus jannaschii (growth temperature optimum 85 degrees C), from Methanobacterium thermoautotrophicum (65 degrees C), and from Methanosarcina barkeri (37 degrees C). Of the four enzymes, that from M. kandleri has the lowest isoelectric point (3.8) and the lowest hydrophobicity of amino acid composition. Besides, it has the highest relative content of glutamate, leucine, and valine and the lowest relative content of isoleucine, serine, and lysine. Some of these properties are unusual for enzymes from hyperthermophilic organisms. They may reflect the observation that the cyclohydrolase from M. kandleri is not only adapted to hyperthermophilic conditions but also to the high intracellular concentrations of lyotrophic salts prevailing in this organism.

Amino Acid Sequence↗
PubMed1998

Estimation of genome sizes of hyperthermophiles.

Genomes of various hyperthermophilic and extremely thermophilic prokaryotes were analyzed with respect to size, physical organization, and 16S rDNA copy number. Our results show that all the genomes are circular, and they are in the size range of 1.6-1.8 Mb for Pyrodictium abyssi, Methanococcus igneus, Pyrobaculum aerophilum, Archaeoglobus fulgidus, Archaeoglobus lithotrophicus, and Archaeoglobus profundus (the two bacteria Fervidobacterium islandicum and Thermosipho africanus possess genomes of 1.5-Mb size). A systematic study of all validly described species of the order Sulfolobales revealed the existence of two classes of genome size for these archaea, correlating with phylogenetic analyses. The Metallosphaera-Acidianus group, plus Sulfolobus metallicus, have genomes of ca. 1.9 Mb; the other members of the order Sulfolobales group possess genome > 2.7 Mb. The special case of stygiolobus azoricus is discussed.

Archaea↗
PubMed2001

The biochemical properties and phylogenies of phosphofructokinases from extremophiles.

The enzyme phosphofructokinase (PFK) is a defining activity of the highly conserved glycolytic pathway, and is present in the domains Bacteria, Eukarya, and Archaea. PFK subtypes are now known that utilize either ATP, ADP, or pyrophosphate as the primary phosphoryl donor and share the ability to catalyze the transfer of phosphate to the 1-position of fructose-6-phosphate. Because of the crucial position in the glycolytic pathway of PFKs, their biochemical characteristics and phylogenies may play a significant role in elucidating the origins of glycolysis and, indeed, of metabolism itself. Despite the shared ability to phosphorylate fructose-6-phosphate, PFKs that have been characterized to date now fall into three sequence families: the PFKA family, consisting of the well-known higher eukaryotic ATP-dependent PFKs together with their ATP- and pyrophosphate-dependent bacterial cousins (including the crenarchaeal pyrophosphate-dependent PFK of Thermoprotetus tenax) and plant pyrophosphate-dependent phosphofructokinases; the PFKB family, exemplified by the minor ATP-dependent PFK activity of Escherichia coli (PFK 2), but which also includes at least one crenarchaeal enzyme in Aeropyrum pernix; and the tentatively named PFKC family, which contains the unique ADP-dependent PFKs from the euryarchaeal genera of Pyrococcus and Thermococcus, which are indicated by sequence analysis to be present also in the methanogenic species Methanococcus jannaschii and Methanosarcina mazei.

Amino Acid Sequence↗
PubMed1990

Conserved N-terminal sequences in the flagellins of archaebacteria.

Methanococcus voltae produces two flagellins of molecular weight 31,000 and 33,000. Amino acid analysis as well as peptide mapping with cyanogen bromide, chymotrypsin and Staphylococcus aureus V-8 protease indicates that the two flagellins are distinct. N-terminal sequencing of the 31,000 Mc. voltae flagellin as well as the 24,000 and 25,000 molecular weight flagellins of Methanospirillum hungatei GP1 shows an extensive homology with the reported N-terminus of the flagellins from Halobacterium halobium, deduced from the nucleotide sequence of the cloned genes. However, the N-termini of all three sequenced methanogen flagellins lack a terminal methionine and start at position 13 from the N-terminus of H. halobium flagellins. This initial 12 amino acid stretch may be a leader peptide which is subsequently cleaved to generate the mature flagellin, which could suggest flagellar assembly in archaebacteria occurs by a mechanism distinct from that in eubacteria. The high degree of conservation of the N-terminus of the flagellins from Mc. voltae, Msp. hungatei and H. halobium suggests an important role for this sequence, and that the archaebacteria share a common mechanism for flagellar biosynthesis.

Amino Acid Sequence↗