FIBRILLIN-RICH MICROFIBRILS - AN X-RAY-DIFFRACTION STUDY OF THE FUNDAMENTAL AXIAL PERIODICITY

Microfibrils are ubiquitous matrix polymers which are thought to provi de elastic properties in all extracellular matrix structures, The majo r component of the elastic microfibrils is the protein fibrillin; its molecular structure is unknown, In electron microscopy, microfibrils a ppear as beaded structures exhibiting a variable periodicity, indicati ng that they may be elastomeric, The X-ray diffraction of fibrillin-ri ch microfibrils in the form of zonular filaments from bovine eyes exhi bits meridional diffraction peaks indexing on a fundamental periodicit y of 55 nm in the relaxed state, The application of a 40% extension pr oduced a lengthening of the periodicity by 3% as judged by alteration of the D spacing of the principal peaks, This effect was shown to be r eversible, Changes in the periodicity of the meridional reflections in dicate changes in the fundamental structure of the microfilaments, but cannot account for all long range elastomeric properties of fibrillin -containing microfibrils. (C) 1997 Federation of European Biochemical Societies.