Department of Infectious, Parasitic and Immunomediated Diseases, Istituto Superiore di Sanità, Rome, Italy.
PLoS One. 2013 Oct 11;8(10):e78090. doi: 10.1371/journal.pone.0078090. eCollection 2013.
The 14-3-3s are small acidic cytosolic proteins that interact with multiple clients and participate in essential cellular functions in all eukaryotes. Available structural and functional information about 14-3-3s is largely derived from higher eukaryotes, which contain multiple members of this protein family suggesting functional specialization. The exceptional sequence conservation among 14-3-3 family members from diverse species suggests a common ancestor for 14-3-3s, proposed to have been similar to modern 14-3-3ε isoforms. Structural features of the sole family member from the protozoan Giardia duodenalis (g14-3-3), are consistent with this hypothesis, but whether g14-3-3 is functionally homologous to the epsilon isoforms is unknown. We use inter-kingdom reciprocal functional complementation and biochemical methods to determine whether g14-3-3 is structurally and functionally homologous with members of the two 14-3-3 conservation groups of the metazoan Drosophila melanogaster. Our results indicate that although g14-3-3 is structurally homologous to D14-3-3ε, functionally it diverges presenting characteristics of other 14-3-3s. Given the basal position of Giardia in eukaryotic evolution, this finding is consistent with the hypothesis that 14-3-3ε isoforms are ancestral to other family members.
14-3-3 蛋白是小的酸性胞质蛋白，与多种客户相互作用，并参与所有真核生物的基本细胞功能。关于 14-3-3 的可用结构和功能信息主要来自高等真核生物，其中包含该蛋白家族的多个成员，表明功能专业化。来自不同物种的 14-3-3 家族成员之间的特殊序列保守性表明 14-3-3 具有共同的祖先，据推测该祖先是类似于现代的 14-3-3ε 同工型。原生动物十二指肠贾第虫（g14-3-3）唯一家族成员的结构特征与该假说一致，但 g14-3-3 是否在功能上与 ε 同工型同源尚不清楚。我们使用种间相互功能互补和生化方法来确定 g14-3-3 是否与后生动物果蝇的两个 14-3-3 保守群的成员在结构和功能上具有同源性。我们的结果表明，尽管 g14-3-3 在结构上与 D14-3-3ε 同源，但在功能上它存在差异，表现出其他 14-3-3 的特征。鉴于贾第虫在真核生物进化中的基础地位，这一发现与 14-3-3ε 同工型是其他家族成员的祖先的假说一致。
