cover illustration The soluble, recombinant plasmepsin I (PM I) from Plasmodium falciparum was successfully expressed in Escherichia coli by fusing the truncated form of PM I to thioredoxin in the pET32b(+) vector. The recombinant protease was capable of autocatalytic activation, and the mature form exhibited dual pH optima for peptide hydrolysis. Interestingly, PM I can exist as monomers and oligomers, and these two states showed different pH dependency and substrate specificity. Molecular modeling indicated salt bridges which were located at the interface of the two monomers of PM I. The formation of salt bridges is proposed to contribute to both the dual pH optima and the activity of aggregates. For details, please see Xiao et al., pp. 625-633.
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