MICROHETEROGENEITY OF ODORANT-BINDING PROTEINS IN THE PORCUPINE REVEALED BY N-TERMINAL SEQUENCING AND MASS-SPECTROMETRY

Several odorant binding proteins (OBP) have been previously purified f rom the nasal mucosa of the old world porcupine Hystrix cristata. In t his paper, we report their N-terminal amino-acid sequences and accurat e molecular weights, as measured by electrospray mass spectrometry. Th e partial amino acid sequences reveal significant similarity with OBPs of other mammalian species and segregate the eight proteins purified into two subclasses. Mass spectrometry has revealed microheterogeneity among the proteins belonging to each of these two groups, suggesting a total number of OBPs of at least nine. The molecular weight differen ces between OBPs cannot be readily accounted for by common post-transl ation modifications and indicate different gene products. Such a large number of different OBPs may represent. further support to an odour d iscriminating role for these proteins. (C) 1997 Elsevier Science Inc.