title: Appendix. Structural predictions on alpha 2-macroglobulin from the amino acid sequence.
abstract: The composite result from three different methods predicts that alpha 2-macroglobulin has a predominant pattern of alternating beta-strands and turns. Only scattered pieces of alpha-helix are present throughout its sequence. Predicted beta-strands constitute 43.8% and helices 8.6%, in fair agreement with circular dichroism spectra. Circular dichroism spectra and sequence data suggest that the tertiary structure of complement component C3b is similar to that of the alpha 2 macroglobulin monomer. At present, the beta-barrel configuration of prealbumin seems to be a better model than those of soybean trypsin inhibitor, serine proteases, and immunoglobulins. A repetitive pattern of disulfide loops could indicate structural units of about 200 residues in size, but this is not supported by amino acid sequence homology. The hydropathic pattern of the sequence reveals numerous examples of predicted immunogenic peptides and detects an approximately 100-residue hydrophobic core region, which could constitute parts of the tentatively assigned consecutive activation cleavage and thiol ester domains. This core is an obvious candidate of rearrangement transfer between the highly exposed bait region and the partly shielded thiol ester site. The presumed intersubunit half-cystine is moderately buried and has two nearby patches of high charge density which could guide the dimeric assembling.
mesh_terms: D000595:Amino Acid Sequence; D004220:Disulfides / Q000032:analysis; D000939:Epitopes / Q000032:analysis; D006801:Humans; D046911:Macromolecular Substances; D011487:Protein Conformation; D000511:alpha-Macroglobulins
chemical_list: D004220:Disulfides; D000939:Epitopes; D046911:Macromolecular Substances; D000511:alpha-Macroglobulins