A protein (M<SUB>r</SUB> 24 kDa) that co-purifies with porcine skin lysyl oxidase (M<SUB>r</SUB> 34 kDa) has been characterised. Five variants of the 24 kDa protein were identified by Mono Q FPLC, as were 4 variants of lysyl oxidase. By amino acid analysis the 24 kDa protein is particularly rich in tyrosine, and isoelectric focussing shows it to be acidic, so the name TRAMP (Tyrosine Rich Acidic Matrix Protein) is used to identify this protein. By amino acid sequence analysis and immunoblotting, TRAMP is unrelated to lysyl oxidase, though it is identical (in all but 4 residues) to a 22 kDa extracellular matrix protein from bovine skin that associates with dermatan sulphate proteoglycan. TRAMP is not a proteoglycan however, as mass spectrometry indicates a molecular mass only 150 Da greater than that predicted from the amino acid sequence, and treatment with a number of deglycosylating enzymes does not alter the electrophoretic migration of the protein. Sequence analysis, mass spectrometry and susceptibility to sulphatase treatment, indicates the presence of sulphated tyrosine residues in TRAMP. Although TRAMP occurs as a quantitatively minor component in skin, it shows a widespread tissue distribution. TRAMP does not appear to affect the activity of lysyl oxidase on an elastin substrate. However turbidity time data, shows that sub-equimolar concentrations of TRAMP accelerate the <i>in vitro</i> formation of fibrils from purified, lathyritic (i.e. non cross-linked) rat skin type I collagen. The fibrils which form are well ordered with a D-periodicity similar to those observed <i>in vivo</i>, though fibrils formed in the presence of TRAMP are significantly thinner. TRAMP binds to collagen fibrils as shown by co-sedimentation, and once formed, fibrils are more resistant to low temperature solubilisation. TRAMP may have a important role in the early, nucleation stages of fibril formation.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:654171 |
| Date | January 1993 |
| Creators | MacBeath, Jonathan Roderick Edward |
| Publisher | University of Edinburgh |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hdl.handle.net/1842/19948 |
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