1 Co-expression of the Plasmodium falciparum molecular chaperone, PfHsp70, improves the heterologous production of the antimalarial drug target GTP cyclohydrolase I, PfGCHI Linda L Stephens 1 , Addmore Shonhai 1# and Gregory L Blatch 1* 1 Department of Biochemistry, Microbiology and Biotechnology, Rhodes University, Grahamstown, 6140, South Africa #Present address: Department of Biochemistry and Microbiology, Zululand University, Kwadlangezwa, 3886, South Africa * Corresponding author: Email Address: g.blatch@ru.ac.za; Telephone: +27 46 603 8262; Fax: +27 46 622 3984 Keywords: molecular chaperone, Plasmodium falciparum, Hsp70, GTP cyclohydrolase I, co- expression, protein folding Abbreviations: Pf, Plasmodium falciparum; GCHI, GTP cyclohydrolase I; Hsp70, heat shock protein 70