Download MS2 Phage Coat Protein—RNA Interaction

MS2 Phage Coat Protein—RNA Interaction
Read the following passage.
This system is being studied for three reasons: (1) it is an example of a sequence-specific RNAprotein interaction, (2) it participates in a well-behaved in vitro capsid assembly reaction, and
(3) it is a good model system to study how protein finds a target on a large RNA molecule.
Available are an X-ray crystal structure of the RNA-protein complex and an NMR structure of
the free RNA hairpin target. Current efforts focus on understanding how the thermodynamic
details of sequence-specific “recognition” is achieved. We have made mutations in all the amino
acids believed to make contact with the RNA and are evaluating the affinity of the mutant
proteins to the normal RNA target as well as to targets that have single atom changes in either
the bases or the phosphodiester backbone. It is already clear that nearly all the contacts predicted
by the co-crystal structure contribute to the total free energy of binding. Thus, unlike several
protein interfaces that have been analyzed in a similar way, there are no “hot spots” that
dominate the affinity. However, we have several examples where affinity and specificity are
defined by structural elements of the RNA in its free form.
--Olke Uhlenbeck, Interdepartmental Biological Sciences, Northwestern University
Comprehension Test:
1. How many reasons are there for studying this system?
2. What is the nature of the in vito capsid assembly reaction?
3. Current research focuses on what details of sequence-specific recognition?
4. How many “hot spots” dominate the affinity?
5. In what form are there examples of RNA where affinity and specificity are defined by
structural elements?