p244

人文的知は深いのか

ここでの科学の特徴付けは大澤真幸，野家啓一，山極寿一による鼎談「いま，なぜ『ヒトの科学』か」(図書2007.2, p2) での野家氏の発言にもとづく．この発言は野家氏の持論であるらしいことが，野家啓一「増補 科学の解釈学」(ちくま学芸文庫) p024-025からわかる．ただし，彼が言う「科学」は著者が言っているような広い意味ではなく「数量的・要素論的自然観」に支えられた近代科学の意味で，その限りにおいて，はもちろんかなり正しい．しかし，このようなものを科学という時代は去ったか去りつつあるだろう．

細胞と自己組織化

F. M. Harold, “Molecules into cells: specifying spatial architecture,” Mol. Microb. Rev.  69 , 544 (2005): 「 生物学的自己組織化は現実であり重要であるが，それが生きた細胞の中で生じるときは，系全体による制限と制御のもとにおかれる．ほんとうにそれ自身を組織化すると言ってよいものは細胞だけである． 」

リボソーム再構成

本文で引用したのはin vitroでの構成の話であるが，in vivoについての最近のレビューは

Keith Connolly and Gloria Culver 　Deconstructing ribosome construction

 Trends Bichem Sci. 34 256 (2009)

*The Nomura 30S subunit assembly map has survived nearly intact. 50S subunit assembly is not as well studied as its counterpart 30S.

*The in vitro analyses of subunit assembly suggest that rRNA falls victim to misfolding during assembly and that r-proteins might initially stabilize these conformations before rearrangement and appropriate folding. The isolation of cold-sensitive Escherichia coli strains suggests that improper folding of 16S rRNA can be detrimental to subunit biogenesis and cell growth.

*The maturation step is not understood well.

30Sの試験管内再構成に関しては，構造の新しい表現法を使った次の総説が詳しい ．

Michael T. Sykes, James R. WilliamsonA Complex Assembly Landscape for the 30S Ribosomal Subunit

ARBP 38 197 (2009)

*Recent work using a combination of RNA footprinting and pulse-chase quantitative mass spectrometry paints a picture of small subunit assembly as a dynamic and varied landscape, with sequential and hierarchical RNA folding and protein binding events finally converging on complete subunits.

* The overall impression of 30S subunit assembly is that of a dynamic and fluid process. Proteins do not simply lock into place in a strict processive manner; they work their way into the network of RNA helices in a multiphasic manner. The 16S rRNA begins folding on its own but reacts and adapts to the influx of ribosomal proteins, adopting new local conformations around them and stabilizing others. There are many parallel folding and binding pathways, each of them proceeding simultaneously toward the final product of a complete 30S subunit.