In this study, we report a strong interaction between two contiguous p
roteolytic fragments of fibronectin, each having a mass of about 16 kD
a. This interaction was stable in 4 M NaCl and 4 M urea and dissociati
on of the two fragments required buffers containing 0.5% sodium dodecy
l sulphate. After purification, these peptides maintained their abilit
y to interact when mixed. One fragment was made up of type III repeat
4 and part of 5, the other by repeat 6 and part of 5. Such strong inte
raction between two fibronectin regions may play a role in fibronectin
conformation as well as during fibronectin fibril formation.