In vitro formation of fine fibrils with a D-periodic banding pattern from type V collagen

Type V collagen was isolated from human placenta by limited pepsin treatment and purified by salt fractionation. A solution of type V collagen was dialyzed at 4 degrees C against phosphate-buffered saline or against 0.02 M Na2HPO4. Aggregates formed under these in vitro conditions from a pure type V collagen solution were examined by electron microscopy. The aggregates were fine flexible fibrils. The fibrils formed during incubation at 25 degrees C were of relatively uniform diameter, 34.8 +/- 9.1 nm and did not show an axial banding pattern. When the specimen was incubated at 37 degrees C, the fibrils were of slightly larger diameter, 38.2 +/- 9.1 nm and almost all the fibrils had the axial repeat pattern of 67 nm. The ability of type V collagen to form banding fibrils is discussed in relation in the localization of the collagen in tissues.