The primary structure of the 2265 residues of bovine plasma fibronectin has been completed. The new sequences reported in this paper are residues 600-868 (269 residues), 1138-1217 (80 residues), 1518-1599 (82 residues) and 1868-2061 (194 residues). These sequences constitute six type I11 homology units and two nonhomologous connecting strands. Thus, there are fifteen type I11 homology units in plasma fibronectin. Evidence for two of the three splice variants found in rat liver cells [Schwarzbauer et al. (1983) Cell 35, 421 -4311 was obtained. No indication of the 'extra' type I11 domain present in some human fibroblast fibronectins [Kornblihtt et al. (1984) EMBO J. 3, 221 -2261 was found. Three carbohydrate groups (two glucosamine-based and one galactosamine-based) were identified, giving a total of eight carbohydrate groups in the longest splice variant of bovine plasma fibronectin. A second free sulfhydryl group (cysteine) was identified. This cysteine, like the first, is in a type I11 homology unit. HPLC patterns of peptides obtained from the C-terminal6-kDa fragment suggested that the interchain bridge pattern of fibronectin is antiparallel. The bovine plasma fibronectin sequence is highly homologous to the human cellular fibronectin sequence deduced from the cDNA sequence [Kornblihtt et al. (1985) EMBO J. 4,1755-17591. Fibronectin is a high-molecular-mass, multidomain glycoprotein found in a soluble form in blood plasma and in an insoluble form in loose connective tissue and basement membranes (reviewed in [l -31). Plasma fibronectin, which is synthesized and secreted by hepatocytes [4], and fibronectin synthesized by cultured fibroblasts are similar but not identical. Differences include carbohydrate content [5], fragmentation pattern [6], antigenicity [7] and number of chains [8, 91. Recently the existence of two fibronectin mRNA species from a human cell line was reported [lo]. One of these coded for an extra domain (ED) of 90 amino acid residues relative to the other mRNA. This ED insert seems to be absent in plasma fibronectin [lo] and may, therefore, account for at least some of the difference between cellular and plasma fibronectin.Plasma fibronectin consists of two subunits, which are linked to each other by two disulfide bonds near the C terminus [ll]. The subunits have a molecular mass of about 225 -250 kDa, that is, they vary in mass by 10 -25 kDa when subjected to SDS/polyacrylamide gel electrophoresis, under reducing conditions. The subunits have identical N-terminal and C-terminal sequences, showing that the difference is not due to limited proteolysis.Six cDNA clones, three from rat liver cells [12] and three from human cell lines [13-151, have been isolated corresponding to five different mRNAs. These differ in another area called IIICS (for type 111 connecting segment) C-terminal to the ED, and this area corresponds to the region in which (EC 3.4.21.19). differences between the two chains of fibronectin have been found (at the protein level) to be located [16-181. Recently the th...

The amino acid sequence of protein Z has been determined from sequence analysis performed on fragments obtained by chemical and enzymatic degradations. The polypeptide consists of a single chain containing 396 amino acid residues (Mr 43 677). Comparison with the vitamin K-dependent plasma proteins reveals an extensive homology. The N-terminal part, containing 13 y-carboxyglutamic acid and one /?-hydroxyaspartic acid residue, is extensively homologous to and of similar length to the light chain of factor X. The remainder of protein Z is homologous to the serine proteases and of similar size to the heavy chain of factor Xa, but of the active site residues only aspartic acid-102 is present. Histidine-57 and serine-195 are replaced in protein Z by threonine and alanine, respectively. The physiological function of protein Z is still uncertain.

The complete amino acid sequences of the heparin-, cell-and DNA-binding domains of bovine plasma fibronectin have been determined. The fragments were generated from the 170-kDa central plasmic fragment by extensive digestion with chymotrypsin, and they contain 268, 300 and 269 amino acid residues, respectively. No half-cystines or cysteines were found in these sequences. A glucosamine-based oligosaccharide group is attached to Asn-108 in the sequence of the DNA-binding domain. Only one of the three types of internal homology found in fibronectin [Petersen et al. (1983)

Four differently modified forms of acyl-CoA-binding protein (ACBP) were identified in ACBP purified from bovine liver. The majority of the purified ACBP was focused at pH 5.9 in isoelectric focusing and could be shown to be N-acetylated ACBP without any further modifications. Two minor peaks were focused at pH 5.25 and 4.85 respectively. Mass spectrometry and sequence determination showed that the pI 5.25 form was acetylated at Lys"8 and that the pI 4.85 form was malonylated in the same position. Furthermore, it could be shown that non-enzymic glycosylation occurred during purification. The acetylated and malonylated variants of ACBP were only found in adult cattle.