"RNA and Protein: Molecules in Mutualism"

Loren Williams, Georgia Institute of Technology
Wednesday, January 10, 2018 - 4:00pm to 5:00pm

We have developed three-dimensional comparative methods that allow us to understand and recapitulate the evolution of the ribosome at the molecular level.1-3 We observe that the ribosome has evolved and is continuing to evolve by accretion, recursively growing by addition then freezing of rRNA expansion segments. Functionality of the ribosome accreted along with structure. In analogy with the recording of history by accretion of growth rings of trees, the ribosome has recorded history. The data support a model in which the ribosome recorded the genesis and evolution of protein folding. Aboriginal polypeptides evolved into globular proteins in a hierarchical process. (i) Short random coil peptides bound to rRNA, and (ii) lengthened over time and coalesced into β-β secondary elements. These secondary elements (iii) accreted and formed tertiary interactions within β-domains. Domains (iv) accumulated and gained complex super-secondary structures composed of mixtures of a-helices and b-strands. Finally, (v) proteins reached out and touched each other to form quaternary interactions. Protein evolution was guided and accelerated by interactions with rRNA.4 rRNA stabilized certain immature and intermediate species, bypassing the immense space of unproductive sequences. The ribosome also reveals the genesis of RNA folding. Aboriginal polynucleotides evolved into globular RNAs in a hierarchical process. The most ancient rRNA is magnesium-rich, non-helical and non-base pairing. In sum, the concepts of mutualism can be extended to molecules and are seen to apply to the relationship between RNA and protein. RNA and protein arose by coevolution as a mutualism pair. Previous to this work, mutualisms were understood to operate on levels of cells, organisms, ecosystems and even societies and economies, but not molecules.

About the Speaker

Loren Williams was born in Seattle, Washington. He received his B.Sc. in Chemistry from the University of Washington where he worked in the laboratory of Martin Gouterman. He received his Ph.D. in Physical Chemistry from Duke University, where he worked the laboratory of Barbara Shaw. He was an American Cancer Society Postdoctoral Fellow first at Duke then at Harvard. From 1988 to 1992 he was an NIH Postdoctoral Fellow with Alexander Rich in the Department of Biology at MIT. He joined the School of Chemistry and Biochemistry at Georgia Tech in 1992 where is he currently a professor. Loren received an NSF CAREER Award in 1995, and a Sigma Xi Award for best paper from Georgia Tech in 1996. He received SAIC Student Advisement Award in 2012, the Petit Institute "Above and Beyond" Award in 2012, Georgia Tech's Faculty Award for Academic Outreach in 2013, and the Georgia Tech College of Science Faculty Mentor Award in 2013. He was director of the NASA Astrobiology Institute funded Ribo Evo Center from 2008 to 2015. MORE

This lecture is part of IAP 2018: Origin of Life Seminar Series
12.091/ 12.S593 | Instructor: Greg Fournier

A series of hosted lectures from leaders in the Origin of Life community, focusing on various dimensions of one of the most challenging problems in the biological and planetary sciences.  Topics will include the origin of cells, metabolism, replication and proteins, as well as the geochemical conditions on the Early Earth that led to prebiotic and early biotic systems.  Enrolled students will attend 4-5 seminars during IAP, actively engage in Q & A sessions with invited speakers in a panel format, and collaborate on creating an Origins of Life online blog resource highlighting the work of invited speakers.


JANUARY 11 | ROOM 54-915 | 4PM
The RNA World: Emergence and Evolution of Functional RNA
Irene A. Chen | University of California, Santa Barbara

JANUARY 29 | ROOM 54-915 | 4PM
What is “I”: The Role of Compartmentalisation in the Origins of Life
Anna Wang | Massachusetts General Hospital, Harvard University

JANUARY 31 | ROOM 54-915 | 4PM
The Planetary Battery for the Origins of Life: The Example of Mars
Vlada Stamenkovic | NASA Jet Propulsion Laboratory, CalTech