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The archaellum: how Archaea swim.

Albers SV, Jarrell KF - Front Microbiol (2015)

Bottom Line: Recent studies on archaeal motility have shown that the archaeal motility structure is unique in several aspects.Although it fulfills the same swimming function as the bacterial flagellum, it is evolutionarily and structurally related to the type IV pilus.This was the basis for the recent proposal to term the archaeal motility structure the "archaellum." This review illustrates the key findings that led to the realization that the archaellum was a novel motility structure and presents the current knowledge about the structural composition, mechanism of assembly and regulation, and the posttranslational modifications of archaella.

View Article: PubMed Central - PubMed

Affiliation: Molecular Biology of Archaea, Institute of Biology II-Microbiology, University of Freiburg , Freiburg, Germany ; Molecular Biology of Archaea, Max Planck Institute for Terrestrial Microbiology , Marburg, Germany.

ABSTRACT
Recent studies on archaeal motility have shown that the archaeal motility structure is unique in several aspects. Although it fulfills the same swimming function as the bacterial flagellum, it is evolutionarily and structurally related to the type IV pilus. This was the basis for the recent proposal to term the archaeal motility structure the "archaellum." This review illustrates the key findings that led to the realization that the archaellum was a novel motility structure and presents the current knowledge about the structural composition, mechanism of assembly and regulation, and the posttranslational modifications of archaella.

No MeSH data available.


The archaeal type IV prepilin peptidases. (A) Crystal structure of FlaK from M. maripaludis. Model was constructed with Pymol (www.pymol.org) using the pdb file 3SOX. The GXDG motif is indicated as well as the localization of the membrane. It is clear that the active site is directed toward the cytoplasmic side of the membrane where cleavage of the class III signal peptide occurs. (B) The N-terminal archaellin sequences of M. maripaludis, S. acidocaldarius, and Hfx. volcanii are shown. The arrow indicates the cleavage site and the blue box delineates the hydrophobic, membrane inserted part of the mature N-terminus of the proteins. FlaK is specific for the archaellins in M. maripaludis, whereas PibD processes a variety of class III signal peptide containing substrates in various archaea.
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Figure 3: The archaeal type IV prepilin peptidases. (A) Crystal structure of FlaK from M. maripaludis. Model was constructed with Pymol (www.pymol.org) using the pdb file 3SOX. The GXDG motif is indicated as well as the localization of the membrane. It is clear that the active site is directed toward the cytoplasmic side of the membrane where cleavage of the class III signal peptide occurs. (B) The N-terminal archaellin sequences of M. maripaludis, S. acidocaldarius, and Hfx. volcanii are shown. The arrow indicates the cleavage site and the blue box delineates the hydrophobic, membrane inserted part of the mature N-terminus of the proteins. FlaK is specific for the archaellins in M. maripaludis, whereas PibD processes a variety of class III signal peptide containing substrates in various archaea.

Mentions: The archaeal prepilin peptidases FlaK/PibD have both been demonstrated by site-directed mutagenesis studies to belong to the unusual family of aspartic acid proteases that also includes the prepilin peptidases of type IV pili systems in bacteria and presenilin, a protease involved in processing amyloid precursor proteins in humans (LaPointe and Taylor, 2000; Bardy and Jarrell, 2003; Szabo et al., 2006; Ng et al., 2007; Hu et al., 2011; Henche et al., 2014). Unlike the case with prepilin peptidases which methylate the N-terminal amino acid of the processed mature pilins (typically, but not always, a phenylalanine; Strom et al., 1993), the archaeal enzymes have not been shown to possess methyltransferase activity. In these polytopic membrane enzymes, two aspartic acid residues, one located within a conserved classic GxGD motif or a new variant GxHyD [Hy represents a hydrophobic amino acid, most commonly alanine, found in about 60% of archaeal sequenced genomes (Henche et al., 2014)], are critical for the peptidase activity (LaPointe and Taylor, 2000; Bardy and Jarrell, 2003; Szabo et al., 2006; Hu et al., 2011). Recently, the crystal structure of the M. maripaludis FlaK was obtained (see Figure 3A; Hu et al., 2011). Analysis of the structure confirmed the presence of six transmembrane helices and demonstrated that FlaK must undergo a conformational change in order to bring the two critical aspartic acid residues, located in transmembrane helix 1 and 4 (the GXGD motif), into close proximity for catalysis.


The archaellum: how Archaea swim.

Albers SV, Jarrell KF - Front Microbiol (2015)

The archaeal type IV prepilin peptidases. (A) Crystal structure of FlaK from M. maripaludis. Model was constructed with Pymol (www.pymol.org) using the pdb file 3SOX. The GXDG motif is indicated as well as the localization of the membrane. It is clear that the active site is directed toward the cytoplasmic side of the membrane where cleavage of the class III signal peptide occurs. (B) The N-terminal archaellin sequences of M. maripaludis, S. acidocaldarius, and Hfx. volcanii are shown. The arrow indicates the cleavage site and the blue box delineates the hydrophobic, membrane inserted part of the mature N-terminus of the proteins. FlaK is specific for the archaellins in M. maripaludis, whereas PibD processes a variety of class III signal peptide containing substrates in various archaea.
© Copyright Policy - open-access
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4307647&req=5

Figure 3: The archaeal type IV prepilin peptidases. (A) Crystal structure of FlaK from M. maripaludis. Model was constructed with Pymol (www.pymol.org) using the pdb file 3SOX. The GXDG motif is indicated as well as the localization of the membrane. It is clear that the active site is directed toward the cytoplasmic side of the membrane where cleavage of the class III signal peptide occurs. (B) The N-terminal archaellin sequences of M. maripaludis, S. acidocaldarius, and Hfx. volcanii are shown. The arrow indicates the cleavage site and the blue box delineates the hydrophobic, membrane inserted part of the mature N-terminus of the proteins. FlaK is specific for the archaellins in M. maripaludis, whereas PibD processes a variety of class III signal peptide containing substrates in various archaea.
Mentions: The archaeal prepilin peptidases FlaK/PibD have both been demonstrated by site-directed mutagenesis studies to belong to the unusual family of aspartic acid proteases that also includes the prepilin peptidases of type IV pili systems in bacteria and presenilin, a protease involved in processing amyloid precursor proteins in humans (LaPointe and Taylor, 2000; Bardy and Jarrell, 2003; Szabo et al., 2006; Ng et al., 2007; Hu et al., 2011; Henche et al., 2014). Unlike the case with prepilin peptidases which methylate the N-terminal amino acid of the processed mature pilins (typically, but not always, a phenylalanine; Strom et al., 1993), the archaeal enzymes have not been shown to possess methyltransferase activity. In these polytopic membrane enzymes, two aspartic acid residues, one located within a conserved classic GxGD motif or a new variant GxHyD [Hy represents a hydrophobic amino acid, most commonly alanine, found in about 60% of archaeal sequenced genomes (Henche et al., 2014)], are critical for the peptidase activity (LaPointe and Taylor, 2000; Bardy and Jarrell, 2003; Szabo et al., 2006; Hu et al., 2011). Recently, the crystal structure of the M. maripaludis FlaK was obtained (see Figure 3A; Hu et al., 2011). Analysis of the structure confirmed the presence of six transmembrane helices and demonstrated that FlaK must undergo a conformational change in order to bring the two critical aspartic acid residues, located in transmembrane helix 1 and 4 (the GXGD motif), into close proximity for catalysis.

Bottom Line: Recent studies on archaeal motility have shown that the archaeal motility structure is unique in several aspects.Although it fulfills the same swimming function as the bacterial flagellum, it is evolutionarily and structurally related to the type IV pilus.This was the basis for the recent proposal to term the archaeal motility structure the "archaellum." This review illustrates the key findings that led to the realization that the archaellum was a novel motility structure and presents the current knowledge about the structural composition, mechanism of assembly and regulation, and the posttranslational modifications of archaella.

View Article: PubMed Central - PubMed

Affiliation: Molecular Biology of Archaea, Institute of Biology II-Microbiology, University of Freiburg , Freiburg, Germany ; Molecular Biology of Archaea, Max Planck Institute for Terrestrial Microbiology , Marburg, Germany.

ABSTRACT
Recent studies on archaeal motility have shown that the archaeal motility structure is unique in several aspects. Although it fulfills the same swimming function as the bacterial flagellum, it is evolutionarily and structurally related to the type IV pilus. This was the basis for the recent proposal to term the archaeal motility structure the "archaellum." This review illustrates the key findings that led to the realization that the archaellum was a novel motility structure and presents the current knowledge about the structural composition, mechanism of assembly and regulation, and the posttranslational modifications of archaella.

No MeSH data available.