Knobs into holes packing is a protein packing Structural motif motif that occurs mainly in alpha helix or coiled coil Protein domain domains . One such example is fibrinogen fibril formation. This motif occurs in coiled coil motifs to maintain and reach a 20 degree left hand crossing angle that is characteristic of coiled coils . This motif looks much like two springs slammed together. See also Helix bundle Further reading http www.cryst.bbk.ac.uk PPS95 course 6 super sec cc.html Cryst http bloodjournal.hematologylibrary.org cgi content abstract 92 9 3302 Blood Journal http www.bijvoet center.nl school seminars Archive 2006 Smith University of Utrecht Source Embase Eilers M., Patel A.B., Liu W. and Smith S.O. 2002 . Comparison of helix interactions in membrane and soluble alpha bundle proteins. Biophysical Journal. 82 5 pp 2720 2736 . protein stub Category Protein structural motifs Biochemistry. 2009 Sep 15 48 36 8656 63. Impaired protofibril formation in fibrinogen gamma N308K is due to altered D D and A a interactions. Bowley SR, Okumura N, Lord ST. Source Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA. ... more details
mergeto Fibril date January 2011 The microfibril is a very fine fibril , or fiber like strand, consisting of glycoproteins and cellulose. It is usually, but not always, used as a general term in describing the structure of protein fiber, examples are hair and spermatozoon sperm tail. Its most frequently observed structural pattern is 9 2 pattern in which two central protofibril s are surrounded by nine other pairs. Cellulose inside plants is one of the examples of non protein compounds that are using this term with the same purpose. Cellulose microfibrils are laid down in the inner surface of the primary cell wall. As the cell absorbs water, its volume increases and the existing microfibrils separate and new ones are formed to help increase cell strength. Synthesis and Function The cellulose is synthesized by cellulose synthase or Rosette terminal complexes which reside on a cells membrane. As cellulose fibrils are synthesized and grow extracellularly they push up against neighboring cells. Since the neighboring cell can not move easily the rosette complex is instead pushed around the cell through the fluid phospholipid membrane. Eventually this results in the cell becoming wrapped in a microfibril layer. This layer becomes the cell wall. The organization of microfibrils forming the primary cell wall are rather disorganized. However, another mechanism is used in secondary cell walls leading to its organization. Essentially, lanes on the secondary cell wall are built with microtubules. These lanes force microfibrils to remain in a certain area while they wrap. During this process microtubules can spontaneously depolymerize and repolymerize in a different orientation. This leads to a different direction in which the cell continues getting wrapped. Marfan Syndrome In Marfan syndrome , there is a defect in fibrillin , the glycoprotein component of microfibrils. ref Ursus Nikolaus Riede, Martin Werner, http books.google.com books?id idR7G osdvQC&printsec frontcover&hl es ... more details
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