Wellems and colleagues subsequently proved, via direct transfection experiments, that mutant PfCG2 did not confer CQ resistance [53] . Simultaneously, the Roepe group measured alkaline pH cyt for some but not all CQR parasites, and early NHE data by that group [54] led to conclusions similar to those of Bray and Ward [51] . Thus, attention then focused on another gene found within the same 36 kbp fragment that harbored pfcg2, namely, pfcrt [55] . Results described in this and additional papers show that PfCRT protein is the ultimate determinant of CQ resistance in P. falciparum malaria, that it resides within the DV membrane, and is not directly involved in pH cyt regulation or plasma membrane NHE (see later section on PfCRT) [56, 57] .