Abstract
The molecular characteristics of soluble extensin from tomato have been investigated. An apparent molecular mass greater than 240 kDa has been previously observed with the shape-dependent method of gel-filtration chromatography [Brownleader and Dey (1993) Planta (Berlin) 191, 457-469]. Tomato extensin is a heavily glycosylated protein that does not migrate into SDS/polyacrylamide gels. This shape-dependent behaviour raises doubts about agreement between the observed apparent mass and the absolute value. The molecular mass measured with matrix-assisted laser desorption/ionization-time-of-flight mass spectrometry (MALDI-TOF MS) was 72.3 kDa, with no evidence of any other species except a doubly charged ion. The sample was therefore considered to be monodisperse under the conditions used. Electron microscopy of soluble extensin showed the presence of particles 40-50 nm in length and 2.0-2.5 nm in width. A minority of these particles showed a central 'kink'. A number of smaller and generally wider particles (20 nm x 2-4 nm) were considered to be folded monomers and larger particles were thought to be dimers. Sedimentation analysis showed that extensin exists in a rapid monomer-dimer equilibrium in the concentration range and buffer used. Sedimentation equilibrium data gave a Kd of 8.5 microM and sedimentation velocity data generated a Kd between 1 and 10 microM. The concentration dependence of the measured sedimentation coefficient was used, together with hydrodynamic bead modelling, to define plausible shapes for monomer and dimer. This suggests that monomeric extensin is an elongated rod of length 40 nm and width 2 nm, which forms staggered dimers of average length 50 nm and width 3 nm. Extensin is an integral component of the primary cell wall. The physical characteristics (size, shape and form) of the rod-like extensin have been evaluated in this paper so that the role that extensin plays in primary cell wall architecture and during plant disease resistance can be more fully understood.
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- Bradley D. J., Kjellbom P., Lamb C. J. Elicitor- and wound-induced oxidative cross-linking of a proline-rich plant cell wall protein: a novel, rapid defense response. Cell. 1992 Jul 10;70(1):21–30. doi: 10.1016/0092-8674(92)90530-p. [DOI] [PubMed] [Google Scholar]
- Brownleader M. D., Ahmed N., Trevan M., Chaplin M. F., Dey P. M. Purification and Partial Characterization of Tomato Extensin Peroxidase. Plant Physiol. 1995 Nov;109(3):1115–1123. doi: 10.1104/pp.109.3.1115. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Brownleader M. D., Dey P. M. Purification of extensin from cell walls of tomato (hybrid of Lycopersicon esculentum and L. peruvianum) cells in suspension culture. Planta. 1993;191(4):457–469. doi: 10.1007/BF00195747. [DOI] [PubMed] [Google Scholar]
- Cooper J. B., Varner J. E. Cross-linking of soluble extensin in isolated cell walls. Plant Physiol. 1984 Oct;76(2):414–417. doi: 10.1104/pp.76.2.414. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Emes C. H., Rowe A. J. Hydrodynamic studies on the self association of vertebrate skeletal muscle myosin. Biochim Biophys Acta. 1978 Nov 20;537(1):110–124. doi: 10.1016/0005-2795(78)90607-4. [DOI] [PubMed] [Google Scholar]
- Esquerré-Tugayé M. T., Lafitte C., Mazau D., Toppan A., Touzé A. Cell Surfaces in Plant-Microorganism Interactions: II. Evidence for the Accumulation of Hydroxyproline-rich Glycoproteins in the Cell Wall of Diseased Plants as a Defense Mechanism. Plant Physiol. 1979 Aug;64(2):320–326. doi: 10.1104/pp.64.2.320. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Gilbert L. M., Gilbert G. A. Sedimentation velocity measurement of protein association. Methods Enzymol. 1973;27:273–296. doi: 10.1016/s0076-6879(73)27014-3. [DOI] [PubMed] [Google Scholar]
- Heckman J. W., Terhune B. T., Lamport D. T. Characterization of native and modified extensin monomers and oligomers by electron microscopy and gel filtration. Plant Physiol. 1988 Mar;86(3):848–856. doi: 10.1104/pp.86.3.848. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Kuntz I. D., Jr, Kauzmann W. Hydration of proteins and polypeptides. Adv Protein Chem. 1974;28:239–345. doi: 10.1016/s0065-3233(08)60232-6. [DOI] [PubMed] [Google Scholar]
- Showalter A. M., Bell J. N., Cramer C. L., Bailey J. A., Varner J. E., Lamb C. J. Accumulation of hydroxyproline-rich glycoprotein mRNAs in response to fungal elicitor and infection. Proc Natl Acad Sci U S A. 1985 Oct;82(19):6551–6555. doi: 10.1073/pnas.82.19.6551. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Stafstrom J. P., Staehelin L. A. A second extensin-like hydroxyproline-rich glycoprotein from carrot cell walls. Plant Physiol. 1987 Jul;84(3):820–825. doi: 10.1104/pp.84.3.820. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Stafstrom J. P., Staehelin L. A. Cross-linking patterns in salt-extractable extensin from carrot cell walls. Plant Physiol. 1986 May;81(1):234–241. doi: 10.1104/pp.81.1.234. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Stafstrom J. P., Staehelin L. A. The role of carbohydrate in maintaining extensin in an extended conformation. Plant Physiol. 1986 May;81(1):242–246. doi: 10.1104/pp.81.1.242. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Stuart D. A., Varner J. E. Purification and Characterization of a Salt-extractable Hydroxyproline-rich Glycoprotein from Aerated Carrot Discs. Plant Physiol. 1980 Nov;66(5):787–792. doi: 10.1104/pp.66.5.787. [DOI] [PMC free article] [PubMed] [Google Scholar]
- van Holst G. J., Varner J. E. Reinforced Polyproline II Conformation in a Hydroxyproline-Rich Cell Wall Glycoprotein from Carrot Root. Plant Physiol. 1984 Feb;74(2):247–251. doi: 10.1104/pp.74.2.247. [DOI] [PMC free article] [PubMed] [Google Scholar]