Vasara Tuija, Keränen Sirkka, Penttilä Merja, Saloheimo Markku
VTT Biotechnology, P.O. Box 1500, Tietotie 2, FIN-02044 VTT, Espoo, Finland.
Biochim Biophys Acta. 2002 Jun 12;1590(1-3):27-40. doi: 10.1016/s0167-4889(02)00197-0.
The 14-3-3 proteins are highly conserved, ubiquitously expressed proteins taking part in numerous cellular processes. Two genes encoding 14-3-3 proteins, ftt1 and ftt2, were isolated and characterised from the filamentous fungus Trichoderma reesei. FTTI showed the highest sequence identity (98% at the amino acid level) to the Trichoderma harzianum protein Th1433. FTTII is relatively distinct from FTTI, showing approximately 75% identity to other fungal 14-3-3 proteins. Despite their sequence divergence, both of the T. reesei ftt genes were equally able to complement the yeast bmh1 bmh2 double disruption. The T. reesei ftt genes were also found to be quite closely linked in the genomic DNA. A C-terminally truncated version of ftt1 (ftt1DeltaC) was first isolated as a multicopy suppressor of the growth defect of the temperature-sensitive yeast secretory mutant sec15-1. Overexpression of ftt1DeltaC also suppressed the growth defect of sec2-41, sec3-101, and sec7-1 strains. Overexpression of ftt1DeltaC in sec2-41 and sec15-1 strains could also rescue the secretion of invertase at the restrictive temperatures, and overexpression of full-length ftt1 enhanced invertase secretion by wild-type yeast cells. These findings strongly suggest that the T. reesei ftt1 has a role in protein secretion.
14-3-3蛋白是高度保守的、广泛表达的蛋白，参与众多细胞过程。从丝状真菌里氏木霉中分离并鉴定了两个编码14-3-3蛋白的基因ftt1和ftt2。FTTI与哈茨木霉蛋白Th1433的序列同一性最高（氨基酸水平为98%）。FTTII与FTTI相对不同，与其他真菌14-3-3蛋白的同一性约为75%。尽管它们的序列存在差异，但里氏木霉的两个ftt基因都同样能够互补酵母bmh1 bmh2双缺失突变体。还发现里氏木霉的ftt基因在基因组DNA中紧密连锁。ftt1的C末端截短版本（ftt1DeltaC）最初作为温度敏感型酵母分泌突变体sec15-1生长缺陷的多拷贝抑制子被分离出来。ftt1DeltaC的过表达也抑制了sec2-41、sec3-101和sec7-1菌株的生长缺陷。在sec2-41和sec15-1菌株中过表达ftt1DeltaC也能在限制温度下挽救蔗糖酶的分泌，而全长ftt1的过表达增强了野生型酵母细胞中蔗糖酶的分泌。这些发现强烈表明里氏木霉的ftt1在蛋白质分泌中起作用。
