Model of fibronectin tertiary structure based on studies of interactions between fragments

Abstract

Human plasma fibronectin aggregates in solution and is thought to form fibrils on cell surfaces, perhaps by self-associating and by interacting with other components such as proteoglycans. We have localized the self-association domains by testing the ability of various fragments of fibronectin to interact with each other. Complexation between fluorescamine-labeled fragments and unlabeled fragments or whole molecules was assessed by gel filtration high-performance liquid chromatography. The fragments studied included nonoverlapping fragments that are situated on the fibronectin polypeptide chain in the following order, beginning from the amino terminus: the 29-, 50-, 120-, 35-, and 25-kDa fragments, as well as multiple-domain fragments of 72 kDa containing the 29- and 50-kDa segments, a fragment of 150 kDa containing the 120- and 35-kDa segment, a fragment of 190 kDa containing the 120- and 35-kDa segments, a fragment of 190 kDa containing the 50-, 150-, and 25-kDa segments, and a 45-kDa fragment containing the 35-kDa segment. The amino-terminal 29-kDa fragment bound to the carboxyl-terminal heparin-binding (Hep II) 35-kDa fragment as well as the 150- and 190-kDa fragments that contain the 35-kDa segment. On the other hand, carboxyl-terminal 35- and 45-kDa Hep II containing fragments bound to each other as well as to amino-terminal 29- and 72-kDa fragments and to the 190-kDa fragment. Further, the 25-kDa carboxyl-terminal fibrin-binding fragment bound the 190-kDa fragment, the only fragment containing the 25-kDa segment.(ABSTRACT TRUNCATED AT 250 WORDS)

Potential regulation of cartilage metabolism in osteoarthritis by fibronectin fragments

“…Therefore, throughout this review the term Fn-f will be used generically. The typical Fn-fs studied by us are generated by sequential cathepsin D and thrombin digestion of human plasma Fn (56,60,61) and are active on bovine (56), human knee (62,65), rabbit and rat cartilage explant cultures (unpublished). Similar cathepsin D and thrombin generated Fn-fs from rabbit plasma Fn, bovine plasma Fn, rat plasma Fn or guinea pig plasma Fn are equally active on bovine cartilage (unpublished).…”

“…In this model, the fibrils are initially formed through domain to domain interactions involving the interaction of the domains of the most potent chondrolytic Fn-f, the 29-kDa Fn-f, with domains of Fn having the type III homology structures found in the 140-kDa cell-binding Fn-f. We reported years ago that the 29-kDa aminoterminal Fn-f interacted with the 140-kDa Fn-f in polymerization reactions (60,121,122).…”

A 70-kDa amino-terminal fibronectin fragment supports gelatin binding to macrophages and decreases gelatinase activity

“…Their formation at sites of injury is thought to result from regulated protease activity [4,19,20]. Proteases are certainly required for wound repair and the formation of fibronectin fragments may optimize such processes by initiating biological responses that can be quite different from those expressed by the intact fibronectin molecule [7,[21][22][23][24]. We recently reported that intact fibronectin and two gelatin-binding fibronectin fragments supported in vitro interaction between soluble 125 I-radiolabeled gelatin and macrophages [1].…”

The measurement of the rotational diffusion coefficient of bovine plasma fibronectin by electric birefringence technique

“…We suggest a new model made from the distribution over a sphere of compact domains arranged in a way discussed by Homandberg et al [35]. This model, in contrast to flexible structures proposed by others , would fit the hydrodynamic data.…”