Final answer:
Repressors are proteins that bind to specific DNA regions to suppress gene transcription in response to stimuli. If MetA or MetC function like the lac operon repressor by binding to operator sites and inhibiting transcription, they would act as gene repressors.
Step-by-step explanation:
To determine which proteins are likely to act as gene repressors, we must understand the roles of regulatory molecules in prokaryotic cells, specifically the function of repressors in gene expression. Repressors are proteins that bind to operator regions and prevent transcription of a gene in response to an external stimulus.
Without mentioning specific proteins MetA, MetB, or MetC, general knowledge states that repressors work by blocking RNA polymerase from transcribing the operon. An example of a repressor in action is the lac operon. In the absence of lactose, the repressor protein binds tightly to the operator DNA, preventing transcription. In contrast, activators bind to the promoter site to increase transcription. Thus, if MetA or MetC function similarly to the repressor protein in the lac operon, they would be considered gene repressors since they would inhibit transcription.