Figure 1
![The crystal structure of the rabbit skeletal muscle SERCA1 showing the area around the thapsigargin-binding pocket composed of M3 helix (yellow), M5 helix (pink), and M7 helix (brown). The structure was modeled using the PyMOL Molecular Graphics System software (Schr dinger, New York, NY, USA) (available from www.pymol.org) to view the proposed catalytic site of the thapsigargin using the PDB entry 1IWO [25]. Artemisinin derivatives, which share some structural similarity with thapsigargin, were modeled and found to interact with the same regions of the Plasmodium falciparum ATPase6 protein [6, 8]. In addition, the majority of the coding sequence for these helices are conserved in the Plasmodium species, and the E255 in SERCA1 is a corresponding residue of the L263 in the pfATPase6 protein [6, 8].](https://sciendo-parsed.s3.eu-central-1.amazonaws.com/64706b4783f1392090d6937c/j_1905-7415.0903.401_fig_001.jpg?X-Amz-Algorithm=AWS4-HMAC-SHA256&X-Amz-Content-Sha256=UNSIGNED-PAYLOAD&X-Amz-Credential=ASIA6AP2G7AKA5RA4DHX%2F20251210%2Feu-central-1%2Fs3%2Faws4_request&X-Amz-Date=20251210T091438Z&X-Amz-Expires=3600&X-Amz-Security-Token=IQoJb3JpZ2luX2VjEAgaDGV1LWNlbnRyYWwtMSJHMEUCIQDUHJ9g1UYjkQDaOck0uFYvEYElDJ1zr0RMZuDMDvcubQIgHpuTw9iW%2B0kBeHd0Gy%2FHzd97Qvpv5JuMuPFykKfhCDAqxQUI0f%2F%2F%2F%2F%2F%2F%2F%2F%2F%2FARACGgw5NjMxMzQyODk5NDAiDGVJnLmWOpWIiCu6VCqZBWwdtv3k9gGqrp7O0rI4%2BRZs%2FTNPP4GrrOlA2LfaOu5egUfKaAee%2BFwzm%2FJYRWui%2F4EE8oaU%2FI6ZWUjJqXqOd1SigGNtdadSTzJF0vpNXqNMOTdm07GcvbAmJTwrmDQ3kHGOy56a9q7w%2BbR%2BLCqvvh61LP7bjI95TMYSbKwrhB3mfV0p8LjbmEACYw2rNTdXTqNjUloq0nitYI%2BFS4P72zzStFOimTiRJJPuiXDA%2BoQxyC%2BDyluTZqbcwsj2pPWooaoedXu0QBMnUD2ajtZMYnx%2F%2FvxYsnyrW2QUoNeOSBc2plMs%2F6S1dUdZZaip9kH1ujSL44ZD11NIWuENlT8k5ueZyO%2BSD6w9FttklNpy7tt00RxSlJQ%2FEKiHEL3oy6Tq2OtELrzxPIu9%2FSAZhQukJTBfHHv08yP%2F%2BeQStdx7JkDKjA9zM6Va%2B5mL%2B1256BehuccWZvm740EzjaxkdocIssvMaaWhNpqHSu7tV7cBHhRBSCj9o1CScfbl5vCBhBodCltoUa8HSK6lJUyY9PgyWfNC02NEiincAtFMmdw69ng7yxi4yZTjQ9mImMIITyNtJtOeF7V68culm8wCddB4JNl%2BY%2F4paF%2Bt7dykAMbTTR0L6BoF0rSy8R8dSfYfHyFlOJSjg9pg6IhRgA3Jg%2FNKWgbYIm3ad9ZFQH8IzFClrkqnZpqOLt5R8Eria%2FmzSqDjXIz7Aq8nOCcFb7OitkO7cKeX0G207tBULaKhIAQk7v6paWXtArC6%2FlM%2BUC0kqgrOnQOQ74Nfgc7XzJatc%2Bzyxdh4Zg6EE156x4nQbmD%2BLDq54PpoelJRC6aKaRDjCoek2C7R%2FHrbBxtsoANw1xa%2FFFjhZZ%2FSZM1G5fGvT%2FTYo1gZsDaKeBKnypNzMLfM5MkGOrEBVnCODUmgrPov8E3FF1Td02MDUSMnDGfCgDE6JjLRGbDgkosoIAUH1cOGCuOgY2%2B%2BGpi0BYCBsepeGW7jxUDEu3zsACknaXMozdcEWNzCW%2B1aK%2FQ2rtjGPcGfFwkzlsYONcplaWRUZvXdKVnhTFKgw4tOrIf94h4R5P9z7RKagmBvo9HqQrn1OaOdcf3vZahVHBVzB%2By5U7Xhc8RiRh7lcGzfaPvdYlS57swzIZwcwAfu&X-Amz-Signature=152a8ca8abe86c735c65831cca46c89dde8c37c83516eee5e8292aace13ab6a7&X-Amz-SignedHeaders=host&x-amz-checksum-mode=ENABLED&x-id=GetObject)
DNA sequences of the forward (F) and reverse (R) primers used in the PCR experiments
| Primer | Sequences |
|---|---|
| M3F | 5′-AGCATGCTGTTATAGAA-3′ |
| M3R | 5′-TGAATTGGATCTGAGAAATGT-3′ |
| M5F | 5′-TAATGGAACGGAGGTAGCTA-3′ |
| M5R | 5′-ACGGGAGCTAAACTGTCAG-3′ |
| M7F | 5′-TCCACCAGAACATGACGTAA-3′ |
| M7R | 5′-AAAAACCAGTACACAAATATTGAGA-3′ |
| 769F | 5′-AAATATGGGAAAAAGACGATTAA-3′ |
| 769R | 5′-TACACGTATACCAGCCATATGG-3′ |
Sequence polymorphisms of pfATPase6 observed in diverse treatments and clinical outcome
| Regimen | Geographical Region | Clinical Outcome | M3 Sequence Compared to 3D7 Clone | Sequence region around 769 residue Compared to 3D7 Clone | M5 Sequence Compared to 3D7 Clone | M7 Sequence Compared to 3D7 Clone |
|---|---|---|---|---|---|---|
| Artesunate monotherapy | Tasanh, Cambodia | ACPR (n = 70) | Identical (n=70) | Identical (n = 70) | Identical (n = 46) Syn (n = 24) | Identical (n = 70) |
| (n = 74) | Failure (n = 4) | |||||
| (D of treatment initiation, D0) | Identical (n = 4) | Identical (n = 4) | Identical (n = 2) Syn (n = 2) | Identical (n = 4) | ||
| Failure (n = 4) | Identical | Identical (n = 4) | Identical (n = 2) | Identical | ||
| (D of failure Df) | (n = 4) | Syn (n = 2) | (n = 4) | |||
| Quinine and tetracycline | Tasanh, Cambodia | ACPR (n = 37) | Identical (n = 37) | Identical (n = 37) | Identical (n = 26) Syn (n = 11) | Identical (n = 37) |
| (n = 37) | Failure (n = 0) | |||||
| (D of treatment initiation, D0) | N/A | N/A | N/A | N/A | ||
| Failure (n = 0) (D of failure Df) | N/A | N/A | N/A | N/A | ||
| Artesunate and mefloquine | Trat, Thailand (n = 53) | ACPR (n = 44) | Identical (n = 42) Unamp (n = 2) | Identical (n = 42) Unamp (n = 2) | Identical (n = 35) Syn (n = 7) Unamp (n = 2) | Identical (n = 43) Unamp (n = 1) |
| Failure (n = 9) | ||||||
| (D of treatment initiation, D0) | Identical (n = 9) | Identical (n = 9) | Identical (n = 9) | Identical (n = 9) | ||
| Failure (n = 9) (D of failure Df) | Identical (n = 9) | Identical (n = 9) | Identical (n = 5) Unamp (n = 4) | Identical (n = 9) |
Three regimens and clinical outcomes from two study sites along the Thai–Cambodian border
| Study Sites | Antimalarial Treatment | Number of cases | |
|---|---|---|---|
| ACPR adequate clinical and parasitological response according to the WHO guidelines for the treatment of malaria assessed at 28 days for patients in Tasanh and 42 days for patients in Trat | Treatment failure as defined by WHO in 2003 | ||
| Tasanh, Cambodia | Artesunate monotherapy 200 mg p.o. once daily × 7 d | 70 | 4 |
| quinine 30 mg base/kg/day p.o. × 7 d; plus | |||
| tetracycline 25 mg/kg/day p.o. × 7d | 37 | 0 | |
| Trat, Thailand | Artesunate 12 mg/kg p.o. once daily × 2 d; plus | ||
| mefloquine 25 mg/kg p.o. in 2 split doses; plus | |||
| primaquine 0.5mg/kg p.o. single dose | 44 | 9 | |
| Total | 151 | 13 | |