Origin & Evolution of Life: November 2009

Ribosomes as Ancient Molecular Fossils

Members of NAI's team at Georgia Tech have a new paper in Molecular Biology and Evolution describing an analysis of ribosomal structure and sequence. Their approach chronicles the ribosome's evolution, effectively interpreting the ribosome as a fossil. Using the highest resolution structures available, of two species that represent disparate regions of the evolutionary tree, they have sectioned the large subunit of each ribosome into concentric shells, like an onion, using the site of peptidyl transfer as the origin. Their results suggest that the structure and interactions of both RNA and protein can be described as changing, in an observable manner, over evolutionary time. [Source: NAI Newsletter]

It is widely accepted that around 2.4 billion years ago, the Earth's atmosphere underwent a dramatic change when oxygen levels rose sharply. Called the "Great Oxidation Event" (GOE), the oxygen spike marks an important milestone in Earth's history, the transformation from an oxygen-poor atmosphere to an oxygen-rich one paving the way for complex life to develop on the planet.

Two questions that remain unresolved in studies of the early Earth are when oxygen production via photosynthesis got started and when it began to alter the chemistry of Earth's ocean and atmosphere.

Date/Time: Monday, November 30, 2009 11:00AM Pacific Speaker: Andrew Pohorille (NASA Ames Research Center)

Abstract: "Follow the water" is the canonical strategy in searching for life in the universe. Conventionally, discussion of this topic is focused on the ability of a solvent to support organic chemistry sufficiently rich to seed life. Although this is a necessary condition for the emergence of life it is far from being sufficient. Perhaps more importantly, solvent must promote self-organization of organic matter into functional structures capable of responding to environmental changes. In biology, they are mostly based on non-covalent interactions (interactions that do not involve making or breaking chemical bonds), strength of which must be properly tuned. If non-covalent interactions were too weak, the system would exhibit undesired, uncontrolled response to natural fluctuations of physical and chemical parameters. If they were too strong kinetics of biological processes would be slow and energetics costly.