P26olf (P26)

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P26olf (P26) was prepared from the olfactory epithelium of Rana catesberiana [55]. P26 has 217 residues. The two putative EF-hands in the first half of P26 are most similar to the two in the second half; as in TCBP this reflects a recent gene duplication. EF-hand 3 is separated from EF-hand 2 by 36 residues that are 60% identical to the C-terminal twenty residues of a rabbitt S100. The expectation value of 0.97 indicates that the alignment is not significant for the entire database but this similarity with another EF-hand protein is interesting. None of the EF-hands are inferred to bind calcium in canonical conformation. However, P26 is purified by elution from phenyl Sepharose (following initial binding in 1.0 mM [Ca2+]) with EGTA. It is possible that domains 1 and 3 have an unconventional coordination as found in domains 1 of S100, ICBP, and HYFL.