Passage
Malaria is caused by the parasite Plasmodium falciparum and is transmitted through a female mosquito bite. Although there are antimalarial treatments available, P. falciparum has become resistant to many of these drugs. P. falciparum cells contain a respiratory organelle called the apicoplast that is necessary for the parasite's survival but is not found in humans. Therefore, a new drug that targets this organelle could be useful in the treatment of malaria.A portion of the apicoplast protein ferredoxin (PfFd) is shown in Figure 1, with certain amino acid residues labeled. In the apicoplast, ferredoxin NADP⁺ reductase (PfFNR) interacts electrostatically with PfFd and catalyzes an electron transfer reaction. A compound that selectively inhibits this interaction could be a beneficial antimalarial agent.
Figure 1 Structure of a portion of PfFdChalcone (Compound 3) is a compound that interacts with PfFd and exhibits antimalarial properties. A series of chalcone derivatives (Compounds 4-8) were synthesized via the aldol condensation shown in Scheme 1, where nucleophilic addition of Compound 1 to Compound 2 is followed by elimination to yield α,β-unsaturated carbonyl molecules, Compounds 3-8.
Scheme 1An inhibition assay was performed to compare chalcone (Compound 3) and its derivatives by determining the extent to which these compounds inhibited electron transfer between PfFNR and PfFd (Table 1) .Table 1 Inhibition of electron transfer assay results
Adapted from H. Suwito et al. "Design and synthesis of chalcone derivatives as inhibitors of the ferredoxin - ferredoxin-NADP+ reductase interaction of Plasmodium falciparum: pursuing new antimalarial agents." Molecules. ©2014 MDPI.
-Which amino acid residue on PfFNR most likely interacts with the residues of PfFd shown in Figure 1?

Question

Passage
Malaria is caused by the parasite Plasmodium falciparum and is transmitted through a female mosquito bite. Although there are antimalarial treatments available, P. falciparum has become resistant to many of these drugs. P. falciparum cells contain a respiratory organelle called the apicoplast that is necessary for the parasite's survival but is not found in humans. Therefore, a new drug that targets this organelle could be useful in the treatment of malaria.A portion of the apicoplast protein ferredoxin (PfFd) is shown in Figure 1, with certain amino acid residues labeled. In the apicoplast, ferredoxin NADP⁺ reductase (PfFNR) interacts electrostatically with PfFd and catalyzes an electron transfer reaction. A compound that selectively inhibits this interaction could be a beneficial antimalarial agent.

Figure 1 Structure of a portion of PfFdChalcone (Compound 3) is a compound that interacts with PfFd and exhibits antimalarial properties. A series of chalcone derivatives (Compounds 4-8) were synthesized via the aldol condensation shown in Scheme 1, where nucleophilic addition of Compound 1 to Compound 2 is followed by elimination to yield α,β-unsaturated carbonyl molecules, Compounds 3-8.

Scheme 1An inhibition assay was performed to compare chalcone (Compound 3) and its derivatives by determining the extent to which these compounds inhibited electron transfer between PfFNR and PfFd (Table 1) .Table 1 Inhibition of electron transfer assay results

Adapted from H. Suwito et al. "Design and synthesis of chalcone derivatives as inhibitors of the ferredoxin - ferredoxin-NADP+ reductase interaction of Plasmodium falciparum: pursuing new antimalarial agents." Molecules. ©2014 MDPI.
-Which amino acid residue on PfFNR most likely interacts with the residues of PfFd shown in Figure 1?

Quizplus · Accepted Answer

11ecba2d_12a1_5415_a3bf_77f55812ce59_MD0008_00 Amino acids have three components: an amino group, a carboxyl group, and a side chain, all of which are bonded to the same carbon atom, known as the α-carbon. Amino acid structures differ only by the makeup of the substituent side chains, which contain different functional groups with specific characteristics. Therefore, amino acids can be classified based on their side-chain characteristics. Some amino acids fall into more than one category (eg, both hydrophilic and basic). Acidic and basic amino acids have negatively and positively charged side chains, respectively. These charged amino acids can experience electrostatic interactions with each other or with other oppositely charged functional groups. Figure 1 shows that PfFd contains the acidic amino acid residues aspartate (Asp, D) and glutamate (Glu, E). The passage states that PfFd and PfFNR experience electrostatic interactions, indicating that the amino acid residues have a positive-negative charge attraction. Therefore, a positively charged basic amino acid residue on PfFNR will most likely interact with the negatively charged acidic residues in PfFd. The only answer choice with a positively charged side chain is arginine. (Choice A) This structure is tryptophan (Trp, W), a hydrophobic amino acid with an uncharged side chain. Because its side chain is uncharged, tryptophan cannot interact with the acidic amino acid residues of PfFd. (Choices B and D) These structures are glutamate (Glu, E) and aspartate (Asp, D), which are acidic amino acids with negatively charged side chains. They will not interact with the negatively charged Glu and Asp residues shown in Figure 1 but will instead repel each other. Educational objective: Amino acids have three components: an amino group, a carboxyl group, and a side chain. The side chains are composed of different functional groups with varying characteristics, allowing the amino acids to be categorized by these characteristics. Positively charged side chains can interact with negatively charged ones, and vice versa.

Passage Malaria Is Caused by the Parasite Plasmodium Falciparum and Is