Table 2.

Flexibility and function of segments of PV RdRp structure

Segment	Residues	Motif or region	Relative flexibilitya	Key residuesb	Function
S1	18–26		+++	Asn18, Pro20, Lys22, Lys24	Template binding
	32–39		++		Opening/closing of NTP channel
	41–53		+++		Opening/closing of NTP channel
S3	96–117	I and G	+++	Leu107, Glu108, Thr114	Template binding and opening/closing of nascent RNA channel
	120–149		+++	Lys127
	157–179	F	+++	Tyr157, Lys159, Asp160, Arg163, Lys167, Arg174, Ile176, Ser179	Triphosphate of NTP and template binding
S4	181–200	II	+	Ser184, Arg188, His199	Template binding
	208–217		+	Asp213	Template binding
	226–227		++
	233–240	A	+++	Asp233, Asp238	2′-OH of NTP and metal B binding
S6	288–292		+	Ser288, Gly292	Base of NTP and template binding
	293–312	B	+	Ser294, Asn297	Base of NTP and template binding
	313–317		++		No known function
	323–335	C	+	Tyr326, Gly327, Asp328, Asp329	Primer and metal A binding
	336–345	D	+++
	352–362	D	+++	Lys359	Catalytic general acid
	363–380	E	+++	Lys375, Arg376	Primer binding
S7	381–386		+++		Opening/closing of nascent RNA channel
	391–392		++
	405–423	III	+++	Lys405, Arg408, Asn409, Arg412, His413, Ser416, Leu417, Leu419, Leu420	Template and primer binding and opening/closing of nascent RNA channel
	426–461		+++

^aThe peaks in the PCA plot were identified with respect to the immediate boundary regions. Relative flexibility is assigned as follows: +++, relative displacement > 4-fold; ++, 4-fold > relative flexibility > 3-fold; and +, 3-fold > relative flexibility > 2-fold.

^bResidues that are important for the functions defined in the last column. However, there are no known functions for residues 313–317, which showed conserved dynamics in the studied RdRps.