Mycoplasma hyopneumoniae surface proteins Mhp385 and Mhp384 bind host cilia and glycosaminoglycans and are endoproteolytically processed by proteases that recognize different cleavage motifs
P97 and P102 paralogues occur as endoproteolytic cleavage fragments on the surface of Mycoplasma hyopneumoniae that bind glycosaminoglycans, plasminogen, and fibronectin and perform essential roles in colonization of ciliated epithelia. We show that the P102 paralogue Mhp384 is efficiently cleaved at an S/T-X-F↓X-D/E-like site, creating P60384 and P50384. The P97 paralogue Mhp385 is inefficiently cleaved, with tryptic peptides from a 115 kDa protein (P115385) and 88 kDa (P88385) and 27 kDa (P27385) cleavage fragments identified by LC–MS/MS. This is the first time a preprotein belonging to the P97 and P102 paralogue families has been identified by mass spectrometry. The semitryptic peptide 752IQFELEPISLNV763 denotes the C-terminus of P88385 and defines the novel cleavage site 761L-N-V↓A-V-S766 in Mhp385. P115385, P88385, P27385, P60384, and P50384 were shown to reside extracellularly, though it is unknown how the fragments remain attached to the cell surface. Heparin- and cilium-binding sites were identified within P60384, P50384, and P88385. No primary function was attributed to P27385; however, this molecule contains four tandem R1 repeats with similarity to porcine collagen type VI (α3 chain). P97 and P102 paralogue families are adhesins targeted by several proteases with different cleavage efficiencies, and this process generates combinatorial complexity on the surface of M. hyopneumoniae.
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