fibronectin type III domain or F3 module

Introduction

One of 3 types of internal repeats found in the plasma protein fibronectin. Its tenth fibronectin type 3 repeat contains an RGD cell recognition sequence in a flexible loop between 2 strands. Approximately 2% of all animal proteins contain the FN3 repeat; including:

• extracellular & intracellular proteins
• membrane spanning cytokine receptors
• growth hormone receptors
• tyrosine phosphatase receptors
• adhesion molecules
• other proteins

FN3-like domains are also found in bacterial glycosyl hydrolases.

Three F3 modules form heparan sulfate-binding domain of fibronectin. However, Fibronectin has 15-17 such domains distributed in 3 molecular regions, the majority of which do not appear essential for heparan sulfate binding. The F3 module is absent from fibronectin secreted by hepatocytes.

More general terms

• fibronectin module