Theoretical origin of life;original protein building blocks? (Introduction)

by David Turell , Sunday, January 28, 2018, 00:54 (2280 days ago) @ David Turell

Computer analysis of living proteins has found four basic protein building blocks aht may have been at the origin of life:

http://www.latimes.com/science/sciencenow/la-sci-sn-legos-of-life-20180122-story.html

"By "smashing" proteins and looking at the broken bits, scientists at Rutgers University say they've discovered four basic building blocks that can be stacked like Legos to build all kinds of different proteins.

***

"Many scientists think that some of the earliest forms of life would have hung out where natural electric currents exist — at the bottom of the sea floor, for example, where hydrothermal vents spew material into the ocean.

"Ancient microbes would have needed special proteins to take advantage of those energy sources. These metal-bearing "metalloproteins" would have been able to carry and move electrons around in specific ways. But what exactly did such proteins look like, some 4 billion years ago?

"It's hard to judge by what's in modern-day microbes because their proteins are pretty complex, Nanda said. He pointed to proteins like nitrogenase, an essential enzyme that takes nitrogen and makes ammonia, which is then used to make DNA and amino acids.

"You couldn't imagine that complex nanomachine just emerging out of the primordial soup and just coming into existence," Nanda said. "There had to have been simpler intermediates. But the challenge is we don't have any fossil record of what proteins look like. All we have is the modern proteins, and we have to somehow infer what the simpler proteins may have looked like." (my bold)

***

"the scientists were able to pick out four useful pieces — modules made up of around 60 to 100 amino acids. Each one can carry electrons or carry out reactions but uses different metals (such as copper, iron, nickel or manganese) or puts those metals in different configurations.

"The scientists think the oldest of the four is the one with a cube-shaped cluster of four irons and four sulfurs. That's because this subunit would be very handy for harvesting energy around hydrothermal vents, which are known to host life-like chemical reactions even when living things aren't around. That kind of chemistry could have made it much easier for microbes with the right kinds of electron-shuttling proteins to thrive, the thinking goes.

***

"'We really are only looking at a very small subset of proteins, the ones that are involved in electron transfer," Nanda said.

These smash-and-search methods could be used to find shared building blocks within other groups of proteins beyond the electron-transfer group, he added.

"The scientists also want to chop up those four subunits of 60 to 100 amino acids and find even smaller, simpler essential pieces within them, he said. The simpler the unit, the closer it might be to those primordial proteins."

Comment: Note my bold. How did giant enzyme molecules get created? And where did all the amino acids come from. Only some which can be functional are known to arrive by meteorites. Life still looks miraculous.