7-S collagen: characterization of an unusual basement membrane structure.

摘要: A new type of collageneous structure, tentatively named 7-S collagen, was isolated from a mouse tumor basement membrane, and human placenta, bovine lens capsule kidney. The protein solubilized the tissues by limited digestion with pepsin or trypsin could easily be separated other because its resistance towards further degradation bacterial collagenase at 20 degrees C. collagen showed an amino acid composition typical membrane contained 22% carbohydrate mainly as glucosyl-galactosyl bound to hydroxylysine but also some mannose glucosamine. Ultracentrifugal analysis demonstrated that proteins were homogeneous sedimentation coefficient about 7.2 S molecular weight 360,000 both in phosphate buffer pH 7 6 M guanidine. peptide triple helical shown circular dichroism exhibited biphasic melting profile indicating two conformationally distinct domains tm = 48 C 70 more stable domain fragment (Mr 225,000) after second 37 This all disulfide bonds (42 Cys/1,000 residues) original molecule. Electron microscopy rod-like structure agreement hydrodynamic properties collagen. dimensions these peptides 3 X 95 nm (long form) 2.4 40-50 (short form). Complete reduction under denaturing conditions produced several polypeptide chains range 27,000-153,000 which differ each Mr increments 25,000-27,000. Separation on agarose did not reveal any simple stoichiometric relationship are either cross-linked represent fragments during proteolytic treatments. non-denaturing lowered thermal transiton helix change except when exposed dissociating solvents. collagens potent immunogens characterized radioimmunoassays. Antigenicity slightly reduced denaturation while larger decrease. Proteins obtained various sources immunological relationships although interspecies differences affinity exist. No only little cross-reaction observed IV V data indicate is unique component membranes shows compact than proteins.