Wong Philip, Houry Walid A
Department of Biochemistry, University of Toronto, 1 King's College Circle, Medical Sciences Building, Toronto, Ont., Canada M5S 1A8.
J Struct Biol. 2004 Apr-May;146(1-2):79-89. doi: 10.1016/j.jsb.2003.11.006.
The prevention of aberrant behavior of proteins is fundamental to cellular life. Protein homeostatic processes are present in cells to stabilize protein conformations, refold misfolded proteins, and degrade proteins that might be detrimental to the cell. Molecular chaperones and proteases perform a major role in these processes. In bacteria, the main cytoplasmic components involved in protein homeostasis include the chaperones trigger factor, DnaK/DnaJ/GrpE, GroEL/GroES, HtpG, as well as ClpB and the proteases ClpXP, ClpAP, HslUV, Lon, and FtsH. Based on recent genome sequencing efforts, it was surprising to find that the Mycoplasma, a genus proposed to include a minimal form of cellular life, do not contain certain major members of the protein homeostatic network, including GroEL/GroES. We propose that, in mycoplasmas, there has been a fundamental shift towards favoring processes that promote protein degradation rather than protein folding. The arguments are based on two different premises: (1) the regulation of stress response in Mycoplasma and (2) the unique characteristics of the Mycoplasma proteome.
蛋白质异常行为的预防对细胞生命至关重要。细胞中存在蛋白质稳态过程，以稳定蛋白质构象、重折叠错误折叠的蛋白质，并降解可能对细胞有害的蛋白质。分子伴侣和蛋白酶在这些过程中发挥主要作用。在细菌中，参与蛋白质稳态的主要细胞质成分包括伴侣蛋白触发因子、DnaK/DnaJ/GrpE、GroEL/GroES、HtpG，以及ClpB和蛋白酶ClpXP、ClpAP、HslUV、Lon和FtsH。基于最近的基因组测序工作，令人惊讶地发现，支原体（一个被认为包含最小形式细胞生命的属）不包含蛋白质稳态网络的某些主要成员，包括GroEL/GroES。我们提出，在支原体中，已经发生了根本性的转变，倾向于促进蛋白质降解而非蛋白质折叠的过程。这些论点基于两个不同的前提：（1）支原体中应激反应的调节；（2）支原体蛋白质组的独特特征。
