Fig. 1

Phylogenetic analysis of human SLRPs and schematic representation of class II and III SLRPs. a The rooted dendrogram shows the phylogenetic relationship between the 18 known human SLRPs with colours displaying the five classes of SLRPs. b Crystal structure of fibromodulin (PDB: 5MX0). Open-Source PyMOL was used for presenting the crystal structure. The fibromodulin structure contains several sugar moieties (dark green) and three disulfide-bridges formed between cysteine residues (yellow) in the N- and C-terminal cysteine motifs. The N-terminus is pointing upwards. Note that the variable N-terminal region of fibromodulin is not visible in the structure due to its disordered structure. The leucine-rich repeat consensus sequence (LXXLXLXXNXL, where L is leucine or another hydrophobic residue, N is asparagine and X is any residue) is shown. The repetition of this motif gives the SLRPs their topology with parallel β-strands on the inner concave face and a variable structure on the outer convex face resulting in an overall curved solenoid structure. c Schematic representation of selected elements in the terminal regions of human class II and III SLRPs. The dots in the dashed lines represent leucine-rich repeats, while solid lines represent the N- and C-terminal regions of the SLRPs. Yellow lines represent termini experimentally known to be sulfated, while the green lines represent termini predicted to be sulfated according to current literature. The letter abbreviations denote the following features: “pQ” indicates an N-terminal glutamine which in vivo will cyclize into pyroglutamate (pQ); “Y” represent tyrosines; “sY” are tyrosine sites for which sulfation has been identified experimentally in humans; “D” and “E” represent the aspartic and glutamic acid residues clustered in the C-terminal region of osteoadherin; “P” and “R” represent the prolines and arginines in the N-terminal region of PRELP