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Mol. Cell. Biol., 01 1995, 69-75, Vol 15, No. 1
AE Adams, W Shen, CS Lin, J Leavitt and P Matsudaira
The actin cytoskeleton is a fundamental component of eukaryotic cells, with
both structural and motile roles. Actin and many of the actin- binding
proteins found in different cell types are highly conserved, showing
considerable similarity in both primary structure and biochemical
properties. To make detailed comparisons between homologous proteins, it is
necessary to know whether the various proteins are functionally, as well as
structurally, conserved. Fimbrin is an example of a cytoskeletal component
that, as shown by sequence determinations and biochemical
characterizations, is conserved between organisms as diverse as
Saccharomyces cerevisiae and humans. In this study, we examined whether the
human homolog can substitute for the yeast protein in vivo. We report here
that two isoforms of human fimbrin, also referred to as T- and L-plastin,
can both substitute in vivo for yeast fimbrin, also known as Sac6p, whereas
a third isoform, I-fimbrin (or I- plastin), cannot. We demonstrate that the
human T- and L-fimbrins, in addition to complementing the
temperature-sensitive growth defect of the sac6 null mutant, restore both
normal cytoskeletal organization and cell shape to the mutant cells. In
addition, we show that human T- and L-fimbrins can complement a sporulation
defect caused by the sac6 null mutation. These findings indicate that there
is a high degree of functional conservation in the cytoskeleton, even
between organisms as diverse as S. cerevisiae and humans.
Copyright © 1995, American Society for Microbiology
Isoform-specific complementation of the yeast sac6 null mutation by human fimbrin
Department of Molecular and Cellular Biology, University of Arizona, Tucson 85721.
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