RNA polymerases?

Question

This is from my lecture notes:

Prokaryotes:

All genes transcribed by a single RNA

polymerase with associated sigma factor.

Core enzyme <--> Holoenzyme

What does the "Core enzyme <--> Holoenzyme" part mean?

Is it that the RNA polymerase core enzyme becomes a holoenzyme when it joins with its sigma factor?

Answer 1

Yes: you have it right on. The core enzyme of 2 alpha, 1 beta and 1 beta&#039; subunits can efficiently make the RNA but cannot accurately find the start of a gene. the sigma subunit joins them to form the holoenzyme (holo=complete) which can recognize the promoter sequence of the gene. There are many different sigma proteins and each helps to recognize different promotors.