Mutant/mutation
The mutant lacks expression of ATP synthase subunit beta, mitochondrial (PbATPβ protein).

Protein (function)
PBANKA_145030 contains Walker A and B motifs, an ATP binding site, and a C-terminal PFAM domain shared by all ATP synthase β subunits. A Clustal Omega multiple sequence alignment with the Arabidopsis thaliana and the mouse ATP synthase β subunit gene revealed large areas of conserved amino acid sequence. The N terminus of the protein product of PBANKA_145030 is predicted to be a mitochondrial targeting peptide. Mitochondrial ATP synthase harvests the proton gradient generated across the inner mitochondrial membrane by mitochondrial electron transport to phosphorylate ADP. ATP synthases comprise multiple subunits assembled into two domains: a membrane-integrated F₀ domain that generates rotation as a consequence of allowing protons to move down the gradient  across the membrane it occupies, and an extrinsic F1 domain that catalyzes attachment of inorganic phosphate to ADP using rotation energy. The F₁ domain comprises α and β subunits, with the stoichiometry α₃β₃, and the β subunit contains the catalytic center for ATP formation. Yeast null mutants for ATP synthase β subunit lose mitochondrial ATPase activity, grow well on glucose but poorly on glycerol, and still form the F₁ domain, albeit without a detectable β subunit.

Phenotype
Phenotype analyses indicate an essential role of the PbATPβ protein for development of zygotes/ookinetes in vivo.

In vitro: Comparable activation of female gametocytes and production of zygotes, and a slight, but significant decrease in ookinete conversion rates for PbATPβKO in comparison with wild type parasites.
In vivo (mosquito midgut): The proportion of PbATPβKO activated females was substantially reduced in vivo (under 2%) compared with wild type (40%). Similarly, the PbATPβKO line generated far fewer zygotes (0%) and ookinetes (0%) in vivo. Failure to activate, generate zygotes, and mature to ookinetes by the PbATPβKO female gametocytes in vivo was also evident in the preponderance of aberrant females in vivo (90%) compared with in vitro (1%). No ookinetes were observed at 22 h.

Additional information
The mitochondria of both the asexual and sexual stages of PbATPβKO parasites accumulate Rhodamine 123, a vital dye incorporated into mitochondria with a proton gradient. Transmission electron microscopy revealed that mitochondria of PbATPβKO asexual blood-stage parasites and gametocytes are indistinguishable from the parental line, having a canonical double membrane, granular contents, and distinct tubular cristae in gametocytes.

PbATPβKO in vitro ookinetes were artificially fed to mosquitoes, and, after 12 d, midguts were checked for oocysts. In 50 mosquitoes from four independent feeds, no oocysts were found.

From the Introduction of the paper describing this mutant:
The production of ATP by most eukaryotes occurs in two phases: (i) glycolysis, which oxidizes glucose into pyruvate; and (ii) oxidative phosphorylation or chemiosmosis, in which pyruvate is fully oxidized into carbon dioxide and water within the mitochondrion. During chemiosmosis, the mitochondrial respiratory chain generates a proton gradient that drives a Rotary turbine, known as ATP synthase, located in the inner mitochondrial membrane. Chemiosmosis produces far more ATP than glycolysis but requires oxygen as a terminal electron acceptor. Blood-stage malaria parasites scavenge glucose from the host via a glucose transporter (1) and feed it into their glycolysis pathway. However, despite having access to oxygen, asexual blood-stage malaria parasites do not undertake appreciable chemiosmosis. Rather, they perform what is termed aerobic glycolysis, converting 93% of scavenged glucose into lactate to supply their ATP. Aerobic glycolysis is favored by rapidly growing cells (e.g., yeasts, cancer cells, bloodstream trypanosomes, and blood-stage malaria parasites) because it can support faster growth than chemiosmosis, the requirement for rapid growth apparently offsetting the low efficiency of glycolytic ATP production when glucose is abundant. Reduced chemiosmosis might also alleviate the production of reactive oxygen species, which could be problematic in conjunction with hemoglobin digestion practiced by blood-stage malaria parasites. Despite
the almost total reliance on anaerobic glycolysis by asexual bloodstage malaria parasites, a small amount of electron transport activity within the mitochondrion is crucial to regenerate ubiquinone required as the electron acceptor for dihydroorotate dehydrogenase, an essential enzyme for pyrimidine biosynthesis, and probably to maintain a proton gradient for essential mitochondrial processes such as protein import. Although the asexual blood-stage malaria parasites rely solely on aerobic glycolysis for energy generation, a small proportion of them undergo conversion to gametocytes, which execute a programmed remodeling of their central carbon metabolism. Gametocytes form in preparation for possible transmission to the insect phase of the life cycle should they be taken up in the blood meal of an anopheline mosquito. They are morphologically very distinct and express different genes to asexual blood-stage parasites, and their mitochondrion enlarges and develops distinct cristae (which are lacking in asexual bloodstage parasite  mitochondria). Gametocytes activate the tricarboxylic acid cycle, oxidizing glucose and also glutamate to prime their mitochondrial electron-transport chain. Initially it was not clear whether malaria parasites had a canonical tricarboxylic acid cycle, electron-transport chain, or ATP synthase complex. Various components were either not identifiable or seemed to have been replaced by noncanonical substitutes. Nevertheless, the current consensus is that tricarboxylic acid cycling, electron transport, and ATP synthesis happen in the parasite mitochondrion, just not very much in asexual blood-stage parasites. Indeed, genetic knockout studies have shown that components of the mitochondrial electron-transport chain are dispensable in blood-stage malaria parasites, so long as the ability to regenerate ubiquinone for pyrimidine synthesis is maintained  Electron transport-defective parasites exhibit a phenotype only in the insect stage, where they are unable to complete their development and cannot transmit back to a vertebrate.

Other mutants
RMgm-1240: A mutant lacking expression of ATP synthase subunit beta, mitochondrial (PbATPβ protein) and expressing YFP fused to the hdhfr selectable marker
RMgm-1241: A mutant lacking expression of ATP synthase subunit beta, mitochondrial (PbATPβ protein) and expressing dtTomato (red fluorescent) protein under the control of the hsp70 promoter.
RMgm-1242: A mutant expressing GFP fused to a targeting sequence for the mitochondrion (the first 240 bp of PbATPβ). The gfp gene is under control of the constitutive eefia promoter and is introduced into the silent p230p locus.