Table 2.

Statistics for fitting of C_α atoms only

Structural unit	Position in asymmetric unit	Sumf	Clash	−Den	Avgds
DI + III	A	3.7	9.5	0.9	7.5
	B	3.6	0.0	0.4	8.2
	C	3.7	2.6	0.4	6.4
DII	A	3.8	0.0	0.0	–
	B	3.9	0.0	0.0	–
	C	3.7	0.0	0.0	–
16V + DI + III	B	3.2	0.0	1.7	–
	C	3.5	0.0	0.0	–
16C	B	2.5	0.0	0.5	7.3
	C	2.4	0.0	1.5	5.5

For designation of molecule position in icosahedral asymmetric unit see Fig. 3. For definition of terms see program EMfit (42). SumF (%) is defined as the average value of density for all C_α atomic positions normalized by the rms deviation from the mean of the map. Clash represents the percentage of atoms in one subunit that have steric clashes with symmetry-related subunits. −Den refers to the percentage of atoms that are positioned in negative density. Avgds (Å) is the average distance between restraining and target positions.