Table 1.

Results of forward genetic screen for ProQ substitutions that disrupt RNA binding. Each row represents a plasmid isolated from the screen one or more times which expressed a variant α-ProQ^FL protein that was expressed at wild-type or greater levels and nevertheless displayed reduced b-galactosidase activity with either cspE or SibB hybrid RNAs. Columns indicate (i) the residues in α-ProQ^FL at which substitutions were found to disrupt RNA binding in B3H screen, (ii) the position of each residue based on the ProQ NTD NMR structure (PDB: 5nb9) (28), either within the core of the protein, on the surface or buried, but on the periphery outside of the core (see Supplementary Figure S10), (iii) the specific amino-acid substitution resulting from mutation in each isolated plasmid and (iv) the number of times this mutated plasmid was isolated in screening against either a MS2^hp-cspE or MS2^hp-SibB RNAs

			Times isolated
ProQ residue	Location in NTD	Substitution	with cspE	with SibB
L17	Core	L17P	1	1
R20	Surface	R20P		1
F21	Buried	F21S		1
C24	Core	C24W	1
		C24R		1
F25	Core	F25C	1
		F25S	2	1
		F25Y		1
L34	Core	L34R	1
		L34Q		1
		L34P		1
K35	Surface	K35E		1
		K35N		1
		K35I		1
G37	Surface	G37V		1
I38	Core	I38S	1
L42	Core	L42S		1
L57	Core	L57S	1
A60	Core	A60D	1
L63	Surface	L63P		1
Y64	Core	Y64C	1
		Y64N	1	1
S66	Surface	S66P	1	1
Y70	Surface	Y70H	2	1
L71	Surface	L71P	2	1
R80	Surface	R80C	1
		R80H	1
		R80S		2
V81	Core	V81D	2	1
D82	Surface	D82Y		1
L83	Core	L83F	1
		L83P		1
G85	Surface	G85D	1	1
L91	Buried	L91Q		1
		L91R	1
Q102	Surface	Q102P		1
L103	Buried	L103P		1
25 residues		37 variants	24×	26×