Maltose utilization in E. coli requires the proteins encoded by genes in three different operons. One operonincludes the genes malE, malF, and malG; the secondincludes malK and lamB; and the genes in the thirdoperon are malP and malQ. The MalT protein is apositive regulator that controls the expression of allthree operons; expression of the malT gene itself iscatabolite sensitive.a. What phenotype would you expect to result from aloss-of-function mutation in the malT gene?b. Do you expect the three maltose operons to containbinding sites for CRP (cAMP receptor protein)?Why or why not?In order to infect E. coli, bacteriophage λ binds to themaltose transport protein LamB (also known as the λreceptor protein) that is found in the outer membraneof the bacterial cell. The synthesis of LamB is induced by maltose in the medium via expression of theMalT protein, as described above.c. List the culture conditions under which wild-typeE. coli cells would be sensitive to infection bybacteriophage λ.d. E. coli cells that are resistant to infection by bacteriophage λ have been isolated. List the types of mutationsin the maltose regulon (the set of all genes regulatedby maltose) that λ-resistant mutants could contain.
Gene Interactions
When the expression of a single trait is influenced by two or more different non-allelic genes, it is termed as genetic interaction. According to Mendel's law of inheritance, each gene functions in its own way and does not depend on the function of another gene, i.e., a single gene controls each of seven characteristics considered, but the complex contribution of many different genes determine many traits of an organism.
Gene Expression
Gene expression is a process by which the instructions present in deoxyribonucleic acid (DNA) are converted into useful molecules such as proteins, and functional messenger ribonucleic (mRNA) molecules in the case of non-protein-coding genes.
Maltose utilization in E. coli requires the proteins encoded by genes in three different operons. One operon
includes the genes malE, malF, and malG; the second
includes malK and lamB; and the genes in the third
operon are malP and malQ. The MalT protein is a
positive regulator that controls the expression of all
three operons; expression of the malT gene itself is
catabolite sensitive.
a. What
loss-of-function mutation in the malT gene?
b. Do you expect the three maltose operons to contain
binding sites for CRP (cAMP receptor protein)?
Why or why not?
In order to infect E. coli, bacteriophage λ binds to the
maltose transport protein LamB (also known as the λ
receptor protein) that is found in the outer membrane
of the bacterial cell. The synthesis of LamB is induced by maltose in the medium via expression of the
MalT protein, as described above.
c. List the culture conditions under which wild-type
E. coli cells would be sensitive to infection by
bacteriophage λ.d. E. coli cells that are resistant to infection by bacteriophage λ have been isolated. List the types of mutations
in the maltose regulon (the set of all genes regulated
by maltose) that λ-resistant mutants could contain.
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