Ice nucleation proteins enable bacteria to nucleate crystallization in supercooled water. Contains 126 imperfect repeats of a consensus octapeptide A-G-Y-G-S-T-X-T; further on a 16-residue and a regional 48-residue periodicity is superimposed. A structural model is suggested in which the ice nucleation protein displays a symmetry related to that of ice. Belongs to the bacterial ice nucleation protein family.