Susceptibility to Dental Caries and the Salivary Proline-Rich Proteins

Table 4

Basic PRP genes and products¹.

Locus	Name of encoded protein^2	Partial	Residues^3
PRB1:	Basic salivary proline-rich protein 1		1–392
		Pe (II-2)	17–91
		Ps2	92–392
		IB-9 (PmF)	91–152
		Ps1 (deletion)^4	92–153; 213–392
		Con2 (deletion)^4	152–194; 214–274
		IB-6 (PmS, P-I)^5	275–392
PRB2:	Basic salivary proline-rich protein 2		1–416
	(Con1 glycoprotein)	IB-1	17–112
		IB-7 (P-G)	113–171^6 or 174^7
		Con1	175–299
		IB-8C (P-F)	299–359
		IB-4 (P-H)	361–416
PRB3:	Basic salivary proline-rich protein 3		1–309
	(Parotid salivary glycoprotein G1)	G1	17–309
PRB4:	Basic salivary proline-rich protein 4		1–310
	(Parotid o protein)	Protein N1	17–39
	(Salivary proline-rich protein II-1)	Glycosylated Pr A	40–177
		IB-5 (P-D)	241–310

¹From Azen et al. [70, Table 1] and from Ayad et al. [31, Table 3] updated from the Protein Knowledgebase website (UniProt.org) which was accessed from GeneCards or Epasy websites.
²There is extensive polymorphism (see text). Many proteins encoded by PRB1 and PRB2 [60], Ps1, Ps2, PmS PmF, Pe, Con2 are not included in the Protein Knowledgebase, or (for Con1) the composition is improperly indicated as an alternative name for the whole gene product, which it is not (see Figure 5).
³First set of numbers for each gene indicates the full length encoded polypeptide of each gene. The numbers beneath indicate the fragments of the polypeptide that are commonly found in parotid saliva secretions. The N-terminal 16 amino acids comprise a secretion signal which is removed prior to secretion (Figure 4).
⁴Deletion of repeating sequences 154–212 or 195–213
⁵Sequence is identical to IB-8c plus IB-4. IB-4 (P-H) is not normally released from IB-6 because residues 333–336 are QSAR (Figure 4). IB-4 (P-H) is normally derived from PRB2 where the last 4 C-terminal amino acids of IB-8c (356–360) are RSAR (see text, Section 6). At this time, Uniprot.org appears to have incorrectly listed P-H as produced by PRB1, but IB4 correctly from PRB2. P-H is an alternative name for IB4 and would only be produced from PRB1 if the codon for Q (residue 333) is mutated to R, an uncommon A to G mutation, or an even less common double mutation.
^6,7Termination codon in PRB2S, or cleavage in PRB2M (see legend to Figure 5).