Odorant-binding proteins of the mouse.

After the isolation of two odorant-binding proteins (OBP-I and OBP-II) from mouse nasal tissue, we have purified two additional OBPs, which bind tritiated 2-isobutyl-3-methoxypyrazine. OBP-III is a homodimer with subunits of M(r) 22,000 and pI 4.2. OBP-IV is a homodimer with subunits of M(r) 21,000 and pI 4.85. N-terminal amino acid sequences indicate that OBP-III is identical in its first 40 amino acids to the mouse urinary protein, MUP-5, (ii) OBP-IV is > 90% identical in its first 30 amino acids to the MUP-4, OBP-II is nearly 80% similar in its first 40 amino acids to OBP-I of the rat, and both subunits of OBP-I are > 50% identical with hamster aphrodisin.