Table 2 Domain used by S. pneumoniae PspC and Hic proteins.

#	Region			Domain	Sub domains	Class	n	Module	Structure		Comment host ligand
1			Known	SP			11
2	N-term		Known	HVD	HVD-A, HVD-B, HVD-C		11		α helix	PspC/Hic specific	Factor H
3			Known	RD	RD-I, RD-II, RD-III		7		α helix		sIGA/plgR
					RD-II	PspC	5		α helix
4			Known	RCD			8		α helix
5		1	New	S_nD/Gs₂	3 Positions		10		Coiled coil
6		2	New	RCE1		PspC	2		α helix		Lactoferrin
7		3	New	RCE2			2		A helix
8		4	New	PspA related		PspC	2		α helix	In PspA
9		5	New	R-type			3		α helix		IgA
10		6	New	EPRD			4		α helix
11		7	New	IgA			4		α helix	S. agalactiae
12		8	New	VS4.2		PspC	1		α helix	Specific
13		9	New	VS11.1		Hic	1		α helix	Specific
14	C-term		Known	PRD	PRD-IA, PRD-1B	PspC	5	Modular	Coiled coil	Also in PspA	Cell wall spanning
			New		PRD-II	PspC	1	Modular	Coiled coil	?
			New		PRD-III	Hic	1	Modular	Coiled coil	?
			New		PRD-IV	Hic	4	Modular	Coiled coil	?
15			Known	Anchor	CBD	PspC	6	Modular	β sheets	Several	Anchor
16			Known		LPsTG	Hic	5		Coiled coil	Many	Anchor

The binding sites for Factor H has been mapped within the Hypervariable Domain of PspC3.1 and that of sIgA and the extracellular domain of pIgR to the RNYPT motif of Repeat Domains I and II. C3, C4BP, Plasminogen, Thrombospondin 1, vitronectin have been shown to bind intact S. pneumoniae and full length PspC and Hic proteins, but their binding sites have not been mapped to specific domains. Binding of Lactoferrin and IgA is proposed based on the homology between PspC and Hic variants and the S. pneumoniae immune escape protein PspA and the sIgA binding protein of S. agalactiae.

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