| Summary: | <i>Magnetospirillum gryphiswaldense </i>MSR-1 is one of a number of species to have a genetic system enabling the biomineralisation of iron in c. 40 linearly arranged organelles within its cell. These magnetosomes are believed to be selectively advantageous to cells as a biological compass that helps to minimise the search for nutrients from a three dimensional environment to a one dimensional environment. The gene, <i>mamK, </i>is part of the genetic system involved in the production of magnetosomes and encodes an amino acid sequence with homology to actin and bacterial cell cycle proteins, such as MreB, ParM and FtsA. Results discussed in this thesis outline <i>in vitro</i> characterisation of recombinant <i>Magnetospirillum gryphiswaldense </i>MSR-1 MamK. MamK was expressed in <i>Escherichia coli </i>with and without an N-terminal His-tag and/or a C-terminal GFP domain or a C-terminal cysteine mutation. In all cases, inclusion bodies were formed. MamK was purified from inclusion bodies and resolubilised. Purified MamK was found to self-associate, as indicted by light-scattering assays, in the presence of divalent cations. In contrast to actin and some other bacterial actin-like proteins polymerisation did not appear to require the presence of NTP; however, ATP and GTP was required for purification by ion exchange column chromatography. Polymerisation did not result in a detectable change in tryptophan fluorescence. Depolymerisation was not readily induced by dilution, but slow depolymerisation occurred in the presence of EGTA, as judged by a decrease in light scattering. Microscopy studies showed that formation of large two-dimensional sheets. These results are consistent with <i>in vivo</i> microscopic studies of MamK where polymerisation has been observed.
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