title: Proteolytic fragments identified with domains of the aspartate chemoreceptor.
abstract: Two proteolytic fragments generated during the preparation of the aspartate receptor from Salmonella typhimurium have been purified. These fragments are the products of a single cleavage by an endogenous protease after amino acid 259 in the sequence of the intact receptor. Proteolytic fragment 1 (PF1) represents amino acids 1-259 (Mr = 29,000); this unit retains the aspartate-binding function of the intact receptor. The second fragment (PF2) includes residues 260-552 (Mr = 31,000) and has the normal sites of reversible methylation for the receptor. Like the purified intact receptor, this fragment can be methylated in vitro, although at a much slower rate. Circular dichroic measurements suggest that both proteolytic fragments contain substantial alpha-helical structure, approximately 95 and 53% for PF1 and PF2, respectively. No beta-structure could be detected in either fragment. Molecular sieve chromatography in the presence of detergent suggests that PF1 occurs as a stable multimer of an order equivalent to that observed for the detergent-solubilized aspartate receptor, i.e. a tetramer (+/- 1). PF2 is found to have a multimeric form which is sensitive to the removal of detergent. It is proposed that these fragments represent structural and functional domains of the aspartate receptor.
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins; D002628:Chemoreceptor Cells / Q000032:analysis*; D002942:Circular Dichroism; D003488:Cyanogen Bromide; D008970:Molecular Weight; D010446:Peptide Fragments / Q000032:analysis* / Q000302:isolation & purification; D017459:Receptors, Amino Acid; D017981:Receptors, Neurotransmitter / Q000032:analysis*; D012486:Salmonella typhimurium / Q000032:analysis; D012995:Solubility; D014357:Trypsin
chemical_list: D001426:Bacterial Proteins; D010446:Peptide Fragments; D017459:Receptors, Amino Acid; D017981:Receptors, Neurotransmitter; C031959:aspartic acid receptor; D014357:Trypsin; D003488:Cyanogen Bromide