Amino acid sequence and disulfide-bridge location of canine haptoglobin.
The complete amino acid sequence and disulfide-bridge location of canine haptoglobin (Hp) were determined by analyzing various fragments produced chemically and/or enzymatically. Canine Hp consists of two light (L) and two heavy (H) chains with 83 and 245 amino acid residues, respectively. It has three potential oligosaccharide-binding sequences, Asn-X-Ser/Thr, one in the L chain and two in the H chain. All of them are glycosylated. Comparison of the amino acid sequences between canine Hp and human Hp shows 68 and 85% homology for L chains and H chains, respectively. About 20% of the canine L chain still retains a carboxyl-terminal arginine residue, which is completely removed during maturation in human L-chain. The half-cystine residue at position 15 in the L chain, which participates in the inter-L chain disulfide bridging in human Hp, has been replaced by a leucine residue in canine Hp. Therefore, an LH unit in canine Hp may be joined to another LH unit by a noncovalent (mainly hydrophobic) interaction to form the complete molecule. The disulfide bridges in canine Hp link Cys-34L to Cys-68L, Cys-72L to Cys-105H, Cys-148H to Cys-179H, and Cys-190H to Cys-220H, as in the case of human Hp.
Kumazaki
T
T
Department of Biochemistry, Faculty of Pharmaceutical Sciences, Hokkaido University.
Urushibara
N
N
Ishii
S
S
D000595:Amino Acid Sequence; D000818:Animals; D004220:Disulfides / Q000737:chemistry*; D004285:Dogs; D006242:Haptoglobins / Q000737:chemistry* / Q000302:isolation & purification; D006801:Humans; D008969:Molecular Sequence Data; D011487:Protein Conformation; D011725:Pyridines / Q000737:chemistry; D051381:Rats; D017386:Sequence Homology, Amino Acid
D004220:Disulfides; D006242:Haptoglobins; D011725:Pyridines