The Psychrophilic Metallome

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It is predicted that the psychrophilic metallome of G. antarctica PI12 is zinc-enriched, with the preference of metal uptake decreasing in the order of Zn > Mg > Ca, Fe > Cu, Mn > Na, K, Co, Ni (Table 2). In general, all the results reported by the three approaches mentioned in this study have showed a higher preference for proteins to incorporate transition metal ions (i.e.: manganese, iron, cobalt, nickel, copper and zinc) compared to the alkali (i.e.: sodium and potassium) and alkaline earth metal ions (i.e.: magnesium and calcium). This phenomenon has been explained by Passerini et al. (2006), in which the alkali and alkaline earth metals would tend to bind with proteins through electrostatic interactions. Meanwhile for the transition metals that usually contain electron pairs in the d orbital, they are more favourable to form coordinate covalent bonds with the protein residue (acting as ligands) donating an electron pair to the metal cations. Thus, there is lower binding affinities for alkali metals to bind with proteins, while alkaline earth metals (contain twice the charge of alkali metals) and transition metals can interact more strongly with proteins. However, the influence of the coordination geometry has to be taken into consideration as some metals have greater affinities towards certain geometry at a particular binding site.

The concentration of the metal ions in the cellular system is a biologically controlled process. It is a relatively complex process with many factors are required to be considered, such as the metal bioavailability, the insertion machinery involved, and the biology of the cell [26]. Therefore, all these physiologically-active metals are necessary to buffer down to a narrow range of concentratio...

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