The origins and developments of sulfation-prone tyrosine-rich and acidic N- and C-terminal extensions of class ll and lll small leucine-rich repeat proteins shed light on connective tissue evolution in vertebrates

Table 1 Tyrosine sulfation site prediction

Class	SLRP (animals)	Positions of predicted tyrosine sulfation sites in sequence alignment and logo (Fig. no.)	Corresponding tyrosine residues in precursor human SLRP	Experimentally confirmed tyrosine sulfation sites in precursor SLRP (species)	References
II	Fibromodulin (amniotes)	2 (Fig. 2)	20	20 (human) / 20 (bovine)	[22]
				38 (bovine)
		26 (Fig. 2)	42
		33 (Fig. 2)	45
		41 (Fig. 2)	53	53 (human) / 53 (bovine)
		46 (Fig. 2)	55	55 (human) / 55 (bovine)
				63 (bovine)
				65 (bovine)
II	Lumican (jawed vertebrates)	3 (Fig. 3)	20	20 (mouse)	[22, 23]
		5 (Fig. 3)	21	21 (mouse)
				23 (mouse)
				30 (mouse)
II	Osteoadherin (bony vertebrates (N-terminal); tetrapods (C-terminal))	3 (Fig. 4)	22		[22]
		9 (Fig. 4)	25
		15 (Fig. 4)	31
		27 (Fig. 4)	39	39 (human)
		427 (Fig. 5)	416	416 (human)
		428 (Fig. 5)	417	417 (human)
II	Keratocan (tetrapods)	9 (Fig. 6)	27	N.D.
III	Mimecan (tetrapods)	13 (Fig. 7)	31	N.D.
III	Mimecan (tetrapods)	26 (Fig. 7)	33	N.D.
III	Epiphycan (bony vertebrates)	16 (Fig. 8)	28	N.D.
		27 (Fig. 8)	33
		53 (Fig. 8)	46
III	Opticin (bony vertebrates)	30 (Fig. 9)	N/A	N.D.
		37 (Fig. 9)	56
		46 (Fig. 9)	65
		52 (Fig. 9)	71

Prediction of tyrosine sulfation sites in the N- and C-terminal regions of human class II and III SLRPs based on the conservation of tyrosine residues and adjacent features promoting tyrosine sulfation. Tyrosines that remained after cut-off are listed with their positions in the MSA and sequence logo representations. The figure with the relevant MSA and logo is indicated in brackets. The corresponding tyrosine residues in the precursor human SLRP are listed and the residues, which are experimentally confirmed as sulfated, are indicated. Studies with identified tyrosine sulfations are cited

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