🧬AP Biology
2. Bacteria rely on specific proteins to maintain homeostasis and carry out metabolic processes (see Figure 2). Protein A is a critical metabolic enzyme found in the cytoplasm of E. coli bacteria. The three-dimensional structure of Protein A is essential for its function.
To investigate the role of a chaperone protein (Chap1) in maintaining the structure of Protein A, scientists engineered a strain of E. coli lacking the gene for Chap1 (Mutant). They compared this to the Wild Type strain, which expresses Chap1. Both strains were incubated at various temperatures for 30 minutes. The scientists then measured the percent of Protein A that remained in its native, functional conformation. The results are shown in Table 1.
Proteins can denature (unfold) when exposed to heat. Chap1 functions by binding to exposed hydrophobic regions of unfolded polypeptides, preventing them from aggregating and allowing them to refold correctly (Figure 1). The mechanism of this interaction is shown in Figure 2.
Figure 1. Mechanistic model: Chap1 binds exposed hydrophobic regions on unfolded Protein A to promote refolding into the native functional conformation
The tertiary structure of Protein A is stabilized by interactions between R-groups. Describe the chemical property of the R-groups of the amino acids that are typically found in the core of a cytoplasmic protein like Protein A.
Using the template in the space provided for your response, construct an appropriate type of graph that represents the data in Table 1. Your graph should be appropriately plotted and labeled.
Based on the data in Table 1, determine the temperature at which the absence of Chap1 has the greatest effect on the stability of Protein A.
Table 1. Percent of Functional Protein A (native conformation) in Wild Type and Chap1-Deletion Mutant E. coli After 30 Minutes at Each Temperature (mean ± 2SE)
Based on Table 1, identify the lowest temperature at which the percent of functional Protein A in the Mutant strain is less than 50%.
Based on Figure 1, predict the effect of a mutation that changes the amino acids in the Nonpolar Binding Surface of Chap1 to charged amino acids.
Scientists claim that the survival of E. coli during fever-like conditions in a host (approximately 40 degrees C) depends on the presence of functional Chap1. Additionally, a new antibiotic called HydroBlock has been developed. HydroBlock is a small nonpolar molecule that can enter the bacterial cell.
Use evidence from the information provided to support the scientists' claim.
Based on Figure 1, explain how the antibiotic HydroBlock might reduce the effectiveness of Chap1.
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