Ohno S
Beckman Research Institute of the City of Hope, Duarte, California 91090.
Anim Genet. 1988;19(4):305-16. doi: 10.1111/j.1365-2052.1988.tb00822.x.
Inasmuch as all events in this universe are governed by multitudes of periodicities, it is a mistake to regard any coding sequence as unique implying the descent from random assemblages of four bases. Instead, each coding sequence is comprised of primordial and derived repeating units. In the case of families of proteins with transmembrane alpha-helices, the primordial repeating units of their coding sequences were base heptamers, thus, giving the heptapeptidic periodicity very conductive to alpha-helix formation to the original polypeptide chains. Even in modern coding sequences for these families of proteins, intact and base-substituted copies of these primordial heptamers are found in more or less even distribution along the entire coding sequence. In addition, there are now locally prominent tandemly recurring units that are only remotely related to primordial heptamers. In the case of Ca++ channel, local prominence of one such nonameric unit gave a unique tripeptidic periodicity to the fourth helix of each unit giving to it a girdle of positively charged residues. All these complex interplays between primordial and derived recurring units that characterize each coding sequence can best be appreciated by their musical transformation. The transformed musical score of a pertinent part of rabbit skeletal muscle Ca++ channel coding sequence is given.
