Biochemical and Proteomic Analysis of the Magnetosome Membrane in Magnetospirillum gryphiswaldense

Abstract

We analyzed the biochemical composition of the magnetosome membrane (MM) in Magnetospirillum gryphiswaldense. Isolated magnetosomes were associated with phospholipids and fatty acids which were similar to phospholipids and fatty acids from other subcellular compartments (i.e., outer and cytoplasmic membranes) but were present in different proportions. The binding characteristics of MM-associated proteins were studied by selective solubilization and limited proteolysis. The MM-associated proteins were further analyzed by various proteomic approaches, including one-and two-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis followed by Edman and mass spectrometric (electrospray ionization-mass spectrometry-mass spectrometry) sequencing, as well as capillary liquid chromatography-mass spectrometry-mass spectrometry of total tryptic digests of the MM. At least 18 proteins were found to constitute the magnetosome subproteome, and most of these proteins are novel for M. gryphiswaldense. Except for MM22 and Mms16, all bona fide MM proteins (MMPs) were encoded by open reading frames in the mamAB, mamDC, and mms6 clusters in the previously identified putative magnetosome island. Eight of the MMPs display homology to known families, and some of them occur in the MM in multiple homologues. Ten of the MMPs have no known homologues in nonmagnetic organisms and thus represent novel, magnetotactic bacterium-specific protein families. Several MMPs display repetitive or highly acidic sequence patterns, which are known from other biomineralizing systems and thus may have relevance for magnetite formation.

Experimental observation of magnetosome chain collapse in magnetotactic bacteria: Sedimentological, paleomagnetic, and evolutionary implications

“…With their technique, no sheath structure was observed even in the wild-type. While AMB-1, MSR-1, and MS-1 are closely related, they do have different populations of magnetosome membrane proteins [47], such that they may have different support structures for their magnetosome chains. An intriguing possibility, however, is that MamJ is required for sheath formation, or is one of many components of the sheath itself.…”

Formation of magnetite by bacteria and its application

“…To elucidate the molecular mechanism of BacMP biomineralization, proteome analyses of BacMP membrane proteins have currently been conducted in M. magneticum AMB-1 (Matsunaga et al 2000b;Okamura et al 2000Okamura et al , 2001Arakaki et al 2003;Tanaka et al 2006), M. gryphiswaldense MSR-1 (Grünberg et al 2001(Grünberg et al , 2004 and M. magnetotacticum MS-1 (Okuda et al 1996), from which numerous novel proteins with potentially crucial roles in BacMP biomineralization have been discovered. In the analysis of BacMP membrane proteins from M. gryphiswaldense MSR-1, approximately 30 proteins were identified; a considerable number of these proteins were found to be assigned in gene clusters located within the magnetosome island (Grünberg et al 2004). A similar examination was attempted with M. magneticum AMB-1, wherein a total of 78 proteins were identified from the surface of its BacMP (figure 3; Tanaka et al 2006).…”

Synthesis, Functionalization, and Design of Magnetic Nanoparticles for Theranostic Applications

“…This circle is an indicative of an organic membrane [266] that mainly consists of phospholipids and proteins. [272] Iron oxide [273] or/and iron sulfide mineral [274] constitute the inorganic core of magnetosomes. Different crystal habits or morphologies of magnetic crystals have been observed in MTB by various forms of electron microscopy.…”