CRYSTAL-STRUCTURE OF THE 10TH TYPE-III CELL-ADHESION MODULE OF HUMAN FIBRONECTIN

The crystal structure of the cell adhesion module of fibronectin (FNIII10)_has been determined at 1·8 Å resolution. A recombinant fragment corresponding to the tenth type III module of human fibronectin was crystallized in space group P21 with a = 30·, b = 35·1 and c = 37·7 A ̊ and β = 107°. The structure was determined by molecular replacement and refined by least squares methods. The crystallographic R-factpr for the final model of the 91 amino acid module plus 56 solvent atoms is 0·18 for 10 to 1·8 Å data. The module consists of two layers of β-sheet, one with three antiparallel strands and the other with four antiparallel strands. The β-sheets enclose a hydrophobic core of 24 amino acid side-chains. The module contains the RGD cell recognition sequence in a flexible loop connecting two β-strands. The tertiary structure of the FNIII10 module has been used to develop a structure-based sequence alignment of 17 type III modules in fibronectin based on the striking conservation of homologous hydrophobic residues. A similar pattern of homologous alternating hydrophobic residues is also evident in a comparison of type III modules in proteins unrelated to fibronectin such as cytokine receptors and muscle proteins. © 1994.