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BIOSYNTHESIS OF HETEROGENEOUS FORMS OF MAMMALIAN BRAIN TUBULIN SUBUNITS BY MULTIPLE MESSENGER RNAs
Author(s) -
Marotta Charles A.,
Strocchi Paola,
Gilbert Jeffrey M.
Publication year - 1979
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1979.tb11725.x
Subject(s) - polysome , reticulocyte , tubulin , messenger rna , biology , translation (biology) , protein biosynthesis , biochemistry , protein subunit , tyrosine , rna , microbiology and biotechnology , microtubule , ribosome , gene
—Heterogeneity among the primary translation products of rat brain tubulin messenger RNA was examined. On two‐dimensional gels native cytoplasmic tubulin from randomly bred rats (PB21) consists of two groups of α tubulin subunits among which the most acidic forms, α 1 and α 2 , are most abundant; and β tubulin consists of a minimum of two species, β 1 and β 2 . In the same group of animals the primary translation products of rat brain tubulin mRNA consist of at least these four subunit forms (α 1 α 2 , β 1 and β 2 ); however, minor basic forms of α subunits were not synthesized. This same result was obtained from a homologous brain protein synthesizing system, a heterologous system prepared from brain polysomes and rabbit reticulocyte initiation factors, and a wheat germ lysate programmed with brain poly A mRNA. A variant form of brain tubulin was found in rats bred monogamously for over 30 generations (MB71 rats). MB71 brain polysomes synthesize overlapping a subunits which migrate in two‐dimensional gels to the α 1 position, and the typical PB21 α 2 is not present. The addition of PB21 brain mRNA to a protein synthesizing system composed of MB71 polysomes plus reticulocyte initiation factors allowed synthesis of the typical α 2 tubulin in addition to the MB71 tubulin subunits. The structural relationship among subunits was examined by radioiodinated peptide mapping. The α subunits are structurally different from the β subunits; however, among the major tyrosine‐containing tryptic peptides no prominent differences were observed between α 1 and α 2 , or between β 1 and β 2 by the radioiodination procedure. The results provide evidence for heterogeneity among the primary translation products of brain tubulin mRNA, and for the existence of multiple functional tubulin genes in rat brain.