23 research outputs found
MamA as a Model Protein for Structure-Based Insight into the Evolutionary Origins of Magnetotactic Bacteria
International audienceMamA is a highly conserved protein found in magnetotactic bacteria (MTB), a diverse group of prokaryotes capable of navigating according to magnetic fields - an ability known as magnetotaxis. Questions surround the acquisition of this magnetic navigation ability; namely, whether it arose through horizontal or vertical gene transfer. Though its exact function is unknown, MamA surrounds the magnetosome, the magnetic organelle embedding a biomineralised nanoparticle and responsible for magnetotaxis. Several structures for MamA from a variety of species have been determined and show a high degree of structural similarity. By determining the structure of MamA from Desulfovibrio magneticus RS-1 using X-ray crystallography, we have opened up the structure-sequence landscape. As such, this allows us to perform structural-and phylogenetic-based analyses using a variety of previously determined MamA from a diverse range of MTB species across various phylogenetic groups. We found that MamA has remained remarkably constant throughout evolution with minimal change between different taxa despite sequence variations. These findings, coupled with the generation of phylogenetic trees using both amino acid sequences and 16S rRNA, indicate that magnetotaxis likely did not spread via horizontal gene transfer and instead has a significantly earlier, primordial origin
Correction: MamA as a Model Protein for Structure-Based Insight into the Evolutionary Origins of Magnetotactic Bacteria
<p>Correction: MamA as a Model Protein for Structure-Based Insight into the Evolutionary Origins of Magnetotactic Bacteria</p
<i>(A)</i> Three ArsTM monomers form the trimeric ring.
<p>This flat ring encloses a ~15 Å diameter inner void. <b><i>(B)</i></b> Interaction surface between two monomers that form the trimeric ring. The forces that stabilise the trimeric ring include salt bridges as well as hydrophobic interactions between the N-terminal of a single monomer to the C-terminal of a nearby monomer in a continuous manner.</p
ArsTM crystal packing, asymmetric unit composition and overall structure.
<p><b><i>(A)</i></b> ArsTM crystal packing and asymmetric unit composition. The molecules are shown in three rotation-related views. <b><i>(B)</i></b> Overlay of all six ArsTM monomers reveals the high degree of structural similarity. The representative ArsTM monomer contains five sequential TPR motifs. The molecule is shown in two views, related by a 90° rotation. <b><i>(C)</i></b> An overlay of representative monomers from ArsTM (green), MamAΔ41<sub>Mbav</sub> (PDB ID: 3VTX, orange) and <i>Magnetospirillum</i> species MamAΔ41<sub>AMB-1</sub> (PDB ID: 3AS5 chain A and B in light pink and brown, respectively) related by a 180° rotation. A high structural similarity of MamAΔ41 between the species can be observed, apart from the helical conformation of the identical His-tag linker sequence remaining after thrombin proteolysis (H11: ELALVPR) seen in the 3AS5 chain B and 3VTX. In addition, a light flexibility is observed at the NTD of the monomers. All images were produced by PyMOL.</p
ConSurf analysis shows a high degree of structural conservation between ArsTM and MamA from alternative species, though this is largely limited to the concave surface and a cluster around the fifth TPR and the C-terminal.
<p>All sequences used in this analysis are shown in the multiple sequence alignment of <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0130394#pone.0130394.s002" target="_blank">S2 Fig</a>.</p
Congruency of the phylogenetic trees based on <i>(A)</i> MamA protein sequences and on <i>(B)</i> 16S rRNA gene sequences that reflect the evolution of MTB.
<p>Scale bars represent the percentage sequence divergence. Bootstrap values at nodes are percentages of 100 replicates. The MTB from <i>Alphaproteobacteria</i> class used in the analyses are: <i>Magnetospirillum magnetotacticum</i> (strain MS-1), <i>Ms</i>. <i>magneticum</i> (AMB-1), <i>Ms</i>. <i>gryphiswaldense</i> (MSR-1), strain SO-1, strain LM-1, <i>Magnetovibrio blakemorei</i> (MV-1), <i>Magnetospira</i> sp. QH-2, strain MO-1, <i>Magnetofaba australis</i> (IT-1) and <i>Magnetococcus marinus</i> (MC-1). Strain SS-5 from the <i>Gammaproteobacteria</i> class is also used. From the <i>Deltaproteobacteria</i> class MTB used include the magnetotactic multicellular prokaryotes <i>Ca</i>. Magnetoglobus multicellularis (MMP) and strain HK-1, <i>Ca</i>. Desulfamplus magnetomortis (BW-1), <i>Desulfovibrio magneticus</i> (RS-1 and FH-1), and strain ML-1. <i>Ca</i>. Magnetobacterium bavaricum (Mbav) and strain MYR-1 of the <i>Nitrospirae</i> phylum was also used. Accession numbers are shown in parenthesis.</p
Circular dichroism measurements of ArsTM (purple) and MamAΔ41 proteins from RS-1 (Blue) Mbav (orange), AMB-1 (green) and MSR-1 (red).
<p>(A) Circular dichroism spectra. (B) Circular dichroism melting curve measurements at 222 nm. Wild type MamAΔ41<sub>RS-1</sub> presents the lowest thermostability, with a melting temperature of ~40°C, while the triple mutated MamAΔ41<sub>RS-1</sub> (ArsTM) exhibits a slightly increased thermostability with a melting temperature of ~ 51°C. MamAΔ41<sub>AMB-1</sub>, MamAΔ41<sub>MSR-1</sub> and MamAΔ41<sub>Mbav</sub> present melting temperatures of ~51, 53 and 65°C, respectively.</p
NTD stabilisation of MamAΔ41 from different species.
<p><b><i>(A)</i></b> Detailed representation of the interactions stabilising the ArsTM NTD. The ArsTM NTD is stabilised by a diverse network of hydrophobic interactions. <b><i>(B)</i></b> Detailed representation of the interactions stabilising the MamAΔ41<sub>Mbav</sub> NTD. The MamAΔ41<sub>Mbav</sub> NTD is stabilised by a diverse network of hydrogen bonds and a single non-conserved salt bridge. <b><i>(C)</i></b> Detailed representation of the interactions stabilising the MamAΔ41<sub>AMB-1</sub> NTD. The MamAΔ41<sub>AMB-1</sub> NTD is stabilised through numerous hydrophobic interactions, a few hydrogen bonds and a single conserved salt bridge. Both NTD domains are shown in two views, related by a 90° rotation.</p