Hydroxycarboxylate transporter

Bandell, M., Ansanay, V, Rachidi, N., et al. (1997) Membrane potential-generating malate (MleP) and citrate (CitP) transporters of lactic acid bacteria are homologous proteins. Substrate specificity of the 2-hydroxycarboxylate transporter family. 7 Bi oZ Chem 272,18140-18146. 

Roots modify their environment quite extensively in many ways. The most important of these are pH change, exudation and microbiological activity in the rhizosphere. Root exudates contain compounds such as hydroxycarboxylic acids and amino acids and these are capable of complexing trace metals. Bowling (1976), Farago (1986) and Streit and Stumm (1993) have discussed the theories of mineral uptake by plant roots the first suggests that there are four links in the uptake chain movement of ions or complexes in the soil to the roots uptake into the root transport across the root to the vascular system and movement to the shoot. 

The chemistry of silicon oxygen compounds with SiOs and SiC>6 skeletons in aqueous solution is of special interest. It has been speculated that such Si(IV) complexes with ligands derived from organic hydroxy compounds (such as pyrocatechol derivatives, hydroxycarboxylic acids, and carbohydrates) may play a significant role in silicon biochemistry by controlling the transport of silicon. 

The results presented here suggest that a rich complex chemistry of pentacoordinate silicon with ligands derived from a-hydroxycarboxylic acids (including tartaric acid), hydroximic acids, and oxalic acid may be developed. As most of these ligands derive from natural products and as some of these X Si-silicon(IV) complexes were shown to exist in aqueous solution, compounds of this formula type are of particular interest it has been speculated in the literature [16] that silicon transport in biological systems might be based on higher coordinate Si species, and complexes such as the title compounds could be of interest as model systems in this respect. 

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