9) What protein represses the expression of aerobic metabolic genes? A) ArcA B)
ID: 176403 • Letter: 9
Question
9) What protein represses the expression of aerobic metabolic genes?
A) ArcA
B) ArcA-P
C) ArcB
D) ArcB-P
E) cytochrome oxidase
10) What chemical reaction is used by ArcB to activate its histidine kinase activity when cells enter anaerobic conditions?
A) phosphorylation by ArcA
B) reduction of pairs of cysteins
C) oxidation of pairs of cysteins
D) methylation by SAM
E) it doesn’t get activated
11) What molecular sensor is used to inactivate the transcriptional regulator FNR?
A) auto-phosphorylation
B) phosphorylation by its partner HK
C) oxidation of an Fe-S cluster
D) reduction of an Fe-S cluster
E) FNR is not a transcriptional regulator
12) Which sensor acts primarily as a kinase of a response regulator in the presence of nitrate, and a phosphatase of that same RR in the presence of excess nitrite?
A) NarX
B) NarQ
C) NarL
D) NarP
E) ArcB
13) What histidine kinase forms disulfide bonds in response to anaerobic conditions?
A) ArcB
B) ArcB~P
C) ArcA
D) ArcA~P
E) none of the above
14) When E. coli is placed in a sealed capillary with galactose as the carbon source, how many migration bands will form?
A) one
B) two
C) three
D) four
E) none
15) When E. coli in placed on an open plate (aerobic) with galactose as the only carbon source, how many migration bands will form?
A) one
B) two
C) three
D) four
E) none
16) When E. coli in placed in a sealed capillary with both glucose and galactose as carbon sources, how many migration bands will form?
A) one
B) two
C) three
D) four
E) none
Explanation / Answer
9. The aerobic metabolic pathway enzymes (TCA cycle enzymes) are mainly dependent on the gene expression levels. These genes are known to be subjected to cAMP-crp mediated catabolite repression and Arc-A, Fnr, Sox RS oxidative stress regulatory system mediated aerobic repression.
Hence the correct answer is the option (A).
10. The reduction of pairs of cysteines is used by ArcB to activate its histidine kinase activity when cells enter in anaerobic conditions.
Hence the correct answer is the option (B).
11. The FNR is the transcription factor that utilizes a [4Fe-4S]2+ cluster to directly sense and respond to oxygen limitation. Under anaerobic conditions, FNR is synthesized as a [4Fe-4S]2+ cluster containing protein. Assembly of the [4Fe-4S]2+ cluster causes spontaneous FNR dimerisation, enabling its specific DNA binding and transcription regulation. Upon being exposed to oxygen, the [4Fe-4S]2+ cluster is rapidly oxidized to a [2Fe-2S]2+ cluster which causes the dissociation of FNR dimer and subsequent loss of specific DNA binding at transcription regulation.
Hence the correct answer is the option (C).
12. Nar X sensor acts primarily as a kinase of a response regulator in the presence of nitrate, and a phosphatase of that same RR in the presence of excess nitrite.
Hence the correct answer is the option (A).
14. The E. coli is placed in a sealed (closed) capillary with galactose as the carbon source will form two migration bands.
Hence the correct answer is the option (B).
15. The E. coli in placed on an open plate (aerobic) with galactose as the only carbon source, will form one migration band.
Hence the correct answer is the option (A).
16. The E. coli in placed in a sealed capillary with both glucose and galactose as carbon sources will from three migration bands.
Hence the correct answer is the option (C).
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