You Are Trying to Identify the Peroxisome-Targeting Sequence in the Thiolase

question 21

Essay

You are trying to identify the peroxisome-targeting sequence in the thiolase enzyme in yeast.The thiolase enzyme normally resides in the peroxisome and therefore must contain amino acid sequences that are used to target the enzyme for import into the peroxisome.To identify the targeting sequences, you create a set of hybrid genes that encode fusion proteins containing part of the thiolase protein fused to another protein, histidinol dehydrogenase (HDH).HDH is a cytosolic enzyme required for the synthesis of the amino acid histidine and cannot function if it is localized in the peroxisome.You genetically engineer a series of yeast cells to express these fusion proteins instead of their own versions of these enzymes.If the fusion proteins are imported into the peroxisome, the HDH portion of the protein cannot function and the yeast cells cannot grow on a medium lacking histidine.You obtain the results shown in Figure 15-5.
Figure 15-5
What region of the thiolase protein contains the peroxisomal targeting sequence? Explain your answer.

---

Definitions:

Pooled Sample Variance

An estimate of the variance of two or more populations under the assumption that they have the same variance, calculated by pooling the variances of these samples.

Independent Samples

Two or more groups of samples that are selected from populations such that the selection of a sample does not influence the selection of the other samples.

Point Estimate

A point estimate is a single value approximation of a population parameter based on sample data.

Population Proportions

The fraction or percentage of the population that has a particular property or characteristic.