Fuerst John A, Sagulenko Evgeny
School of Chemistry and Molecular Biosciences; The University of Queensland St. Lucia; St. Lucia, QLD Australia.
Commun Integr Biol. 2010 Nov;3(6):572-5. doi: 10.4161/cib.3.6.13061. Epub 2010 Nov 1.
Endocytosis is a fundamental process of membrane-trafficking in eukaryotes, but has not been known to occur in bacteria or archaea. The origin of endocytosis is central to the understanding of evolution of the first eukaryotes and their endomembrane systems. In a recent study we have established that an endocytosis-like process for uptake of proteins into cells occurs in a bacterium, Gemmata obscuriglobus, a member of the distinctive phylum Planctomycetes of peptidoglycan-less budding bacteria. Members of this phylum characteristically possess cells divided into compartments separated by internal membranes and in the case of G. obscuriglobus these compartments include one where a double membrane envelope surrounds its nucleoid DNA, as well as an outer ribosome- free region of cytoplasm. Proteins can be internalized by cells from the external milieu and collected into this ribosome-free compartment, and this process is energy-dependent and appears to be receptor-mediated. As in eukaryote endocytosis, internalized proteins are associated with vesicles, and can be subjected to proteolytic degradation. The discovery of this process in a bacterium has significant implications for our understanding of the origins of endocytosis in eukaryotes.
内吞作用是真核生物中膜运输的一个基本过程，但此前人们并不认为它会发生在细菌或古细菌中。内吞作用的起源对于理解最早的真核生物及其内膜系统的进化至关重要。在最近的一项研究中，我们发现一种类似内吞作用的蛋白质摄取过程发生在一种细菌——隐秘球囊菌中，它是独特的无肽聚糖出芽细菌浮霉菌门的一员。该门成员的细胞特征性地被内膜分隔成不同的区室，就隐秘球囊菌而言，这些区室包括一个由双层膜包裹其类核DNA的区室，以及一个外部无核糖体的细胞质区域。蛋白质可以被细胞从外部环境内化并收集到这个无核糖体的区室中，这个过程是能量依赖的，并且似乎是受体介导的。与真核生物的内吞作用一样，内化的蛋白质与囊泡相关，并且可以进行蛋白水解降解。在细菌中发现这一过程对于我们理解真核生物内吞作用的起源具有重要意义。
