近日,，研究者研究發(fā)現(xiàn),，人類生命維持的基本物質(zhì)-蛋白質(zhì)并不在某些火山中的單細胞生物體中存在。研究者研究了類似于細菌的古細菌,，發(fā)現(xiàn)這些古細菌有自己的進化歷史,，相關研究成果刊登在了近日的國際雜志PNAS上。
這種缺失的蛋白質(zhì)命名為SSB,，可以結合DNA免于其受損傷,。研究者Malcolm表示，所有細胞不論微生物細胞還是人類細胞都存在某些共性,。這種蛋白質(zhì)SSB在生命初期的細胞中存在,，并且已經(jīng)延續(xù)了超過35億年了。
然而研究者發(fā)現(xiàn),，在任何生命形式中應當存在的,，而且完全有必要的基因卻在火山中的這種古細菌中缺失了，然而卻出現(xiàn)了一種新的基因,，我們命名為ThermoDBP,。
這項研究發(fā)現(xiàn)對于我們理解地球生命的起源提供了另外一條分支,。而且新發(fā)現(xiàn)的這種基因在生物技術工程和合成生物學中將會有新的應用價值。（生物谷Bioon.com）
編譯自：The basic building blocks of life to be rethought after one discovered to be missing
編譯者：T.Shen
doi:10.1073/pnas.1113277108
PMC:
PMID:
Displacement of the canonical single-stranded DNA-binding protein in the Thermoproteales
Sonia Paytubia,1,2, Stephen A. McMahona,2, Shirley Grahama, Huanting Liua, Catherine H. Bottinga, Kira S. Makarovab, Eugene V. Kooninb, James H. Naismitha,3, and Malcolm F. Whitea,3
ssDNA-binding proteins (SSBs) based on the oligonucleotide-binding fold are considered ubiquitous in nature and play a central role in many DNA transactions including replication, recombination, and repair. We demonstrate that the Thermoproteales, a clade of hyperthermophilic Crenarchaea, lack a canonical SSB. Instead, they encode a distinct ssDNA-binding protein that we term “ThermoDBP,” exemplified by the protein Ttx1576 from Thermoproteus tenax. ThermoDBP binds specifically to ssDNA with low sequence specificity. The crystal structure of Ttx1576 reveals a unique fold and a mechanism for ssDNA binding, consisting of an extended cleft lined with hydrophobic phenylalanine residues and flanked by basic amino acids. Two ssDNA-binding domains are linked by a coiled-coil leucine zipper. ThermoDBP appears to have displaced the canonical SSB during the diversification of the Thermoproteales, a highly unusual example of the loss of a “ubiquitous” protein during evolution.
