Mutant/mutation
The mutant expresses a C-terminal GFP-tagged version of HCS2

Protein (function)
Acetyl-CoA carboxylase (ACC) is a biotin-dependent enzyme. Malaria parasites contain a plant-like ACC, and this is the only protein predicted to be biotinylated in the parasite. We found that ACC is expressed in the apicoplast organelle in liver- and blood-stage malaria parasites; however, it is activated through biotinylation only in the liver stages. Biotin is an essential metabolite in all known free-living organisms. It functions as a CO2 carrier in carboxylation and decarboxylation reactions catalyzed by a small family of enzymes, the biotin carboxylases. Biotin carboxylases participate in central metabolic processes such as gluconeogenesis, lipogenesis, amino acid metabolism, and energy transduction. Bacteria, plants, and some fungi can synthesize biotin de novo from a pimeloyl-CoA precursor, but other organisms acquire biotin from their diet or environment. Regardless of how biotin is acquired, a dedicated ATP-dependent biotin ligase, or holocarboxylase synthetase (HCS), is required to catalyze the covalent attachment of biotin to a specific lysine in the target carboxylase. Perhaps the most unusual feature of biotin metabolism in malaria parasites is the presence of two HCS paralogs (HCS1, HCS2) encoded in the genomes of Plasmodium species.

In the paper evidence is presented that: 
- PfHCS1 and PfHCS2 Are Active Biotin Ligases
- Biotin Is Not Essential for the Survival of Blood-Stage Parasites
- Biotinylated Proteins Cannot Be Detected in Blood-Stage Parasites
- Neither PbHCS1 Nor PbHCS2 Is Required for Blood-Stage Replication or Mosquito-Stage Development
- Loss of PbHCS1 Affects Early Liver-Stage Development
- Deletion of PbHCS1, but Not PbHCS2, Results in the Loss of Liver Stage Protein Biotinylation
- Parasites Lacking PbHCS1 Show Delayed Progression Through Liver Stages in Vivo. Deletion of PbHCS1 Affects Late Liver-Stage Development and Reduces Merosome Production.
- Biotin depletion increases the severity of the developmental defects, demonstrating that parasite and host biotin metabolism are required for normal liver-stage

Phenotype
Immunofluorescence analysis demonstrated that the GFP-tagged HCS1 and HCS2 proteins are not predominantly located in the apicoplast in liver-stage or blood stage parasites. Because of its size, the GFP tag may alter protein trafficking and subcellular location. To address this possibility, we generated HA-tagged parasite lines through double cross-over recombination. Consistent with the results from the GFP-tagged lines, the HA-tagged proteins do not have obvious apicoplast co-localization. This was true at different time points during liverstage development and during blood-stage development.

Additional information
See also mutant RMgm-4413 lacking HCS1 which shows the follwing liver stage phenotype:
Reduced growth of liver stages (At 24 hpi, ΔHCS1 parasites were 3 μm2 smaller, at 48h 53 μm2, at 56h 73 μm2 smaller than  WT controls). Reduced merozoite/merosome formation.
A delay of 2.1 days of the prepatent period after infecting mice with 5.000 sporozoites. Reduced infectivity of merozoites/merosomes produces as measured by blood infections in mice infected with merozoites/merosomes

See also mutant RMgm-4414 lacking HCS2 which shows a normal progression throughout the complete life cycle including normal liver stage development.

Other mutants
See also mutant RMgm-4414 lacking HCS2
See also mutant RMgm-4413 lacking HCS1