logo

Welcome


AboutZoos, Since 2008





201306Apr12:26

Fold­able pro­teins in a high-​salt envi­ron­ment, new clues to the ori­gin of life

Infor­ma­tion
pub­lished 06 April 2013 | mod­i­fied 19 March 2014
Archived

Protein structureA struc­tural biol­o­gist at the Florida State Uni­ver­sity Col­lege of Med­i­cine has made dis­cov­er­ies that could lead sci­en­tists a step closer to under­stand­ing how life first emerged on Earth bil­lions of years ago.

Pro­fes­sor Michael Blaber and his team pro­duced data sup­port­ing the idea that 10 amino acids believed to exist on Earth around 4 bil­lion years ago were capa­ble of form­ing fold­able pro­teins in a high-​salt (halophile) envi­ron­ment. Such pro­teins would have been capa­ble of pro­vid­ing meta­bolic activ­ity for the first liv­ing organ­isms to emerge on the planet between 3.5 and 3.9 bil­lion years ago.

The results of Blaber’s three-​year study, which was built around inves­tiga­tive tech­niques that took more than 17 years to develop, are pub­lished in the jour­nal Pro­ceed­ings of the National Acad­emy of Sci­ences.

The first liv­ing organ­isms would have been micro­scopic, cell-​like orga­ni­za­tions capa­ble of repli­cat­ing and adapt­ing to envi­ron­men­tal con­di­tions — a hum­ble begin­ning to life on Earth.

“The cur­rent par­a­digm on the emer­gence of life is that RNA came first and in a high-​temperature envi­ron­ment,” Blaber said. “The data we are gen­er­at­ing are much more in favour of a protein-​first view in a halophile envi­ron­ment.”

The widely accepted view among sci­en­tists is that RNA, found in all liv­ing cells, would have likely rep­re­sented the first mol­e­cules of life, hypoth­e­sis­ing an “RNA-​first” view of the ori­gin of liv­ing sys­tems from non-​living mol­e­cules. Blaber’s results indi­cate that the set of amino acids pro­duced by sim­ple chem­i­cal processes con­tains the req­ui­site infor­ma­tion to pro­duce com­plex folded pro­teins, which sup­ports an oppos­ing “protein-​first” view.

Another pre­vail­ing view holds that a high-​temperature (ther­mophile) envi­ron­ment, such as deep-​ocean ther­mal vents, may have been the breed­ing ground for the ori­gin of life.

The halophile, or salt-​loving, envi­ron­ment has typ­i­cally been con­sid­ered one that life adapted into, not started in. Our study of the pre­bi­otic amino acids and pro­tein design and fold­ing sug­gests the opposite.
Pro­fes­sor Michael Blaber, Florida State Uni­ver­sity Col­lege of Med­i­cine »

With­out the abil­ity to fold, pro­teins would not be able to form the pre­cise struc­tures essen­tial for func­tions that sus­tain life as we know it. Fold­ing allows pro­teins to take on a glob­u­lar shape through which they can inter­act with other pro­teins, per­form spe­cific chem­i­cal reac­tions, and adapt to enable organ­isms to exploit a given envi­ron­ment.

“There are numer­ous niches that life can evolve into,” Blaber said. “For exam­ple, extremophiles are organ­isms that exist in high tem­per­a­tures, high acid­ity, extreme cold, extreme pres­sure and extreme salt and so on. For life to exist in such envi­ron­ments it is essen­tial that pro­teins are able to adapt in those con­di­tions. In other words, they have to be able to fold.”

Comet and mete­orite frag­ments, like those that recently struck in the Urals region of Rus­sia, have pro­vided evi­dence regard­ing the arrival of amino acids on Earth. Such frag­ments pre­date the earth and would have been respon­si­ble for deliv­er­ing a set of 10 pre­bi­otic (before life) amino acids, whose ori­gins are in the for­ma­tion of our solar sys­tem.

Today the human body uses 20 com­mon amino acids to make all its pro­teins. Ten of those emerged through biosyn­thetic path­ways — the way liv­ing sys­tems evolve. Ten — the pre­bi­otic set — can be made by chem­i­cal reac­tions with­out requir­ing any liv­ing sys­tem or biosyn­thetic path­way.

Sci­en­tific evi­dence exists to sup­port many ele­ments in the­o­ries of abio­gen­e­sis (the emer­gence of life), includ­ing the time frame (around 3.5 to 3.9 bil­lion years ago) and the con­di­tions on Earth and in its atmos­phere at that time. Earth would have been made up of vol­canic land masses (the begin­ning of the for­ma­tion of con­ti­nents), salty oceans and fresh-​water ponds, along with a hot (around 80 degrees Cel­sius) and steamy atmos­phere com­pris­ing car­bon diox­ide and nitro­gen. Oxy­gen would have come later as a by-​product of green plant life and bac­te­ria that emerged.

Using a tech­nique called top-​down sym­met­ric decon­struc­tion, Blaber’s lab has been able to iden­tify small pep­tide build­ing blocks capa­ble of spon­ta­neous assem­bly into spe­cific and com­plex pro­tein archi­tec­tures. His recent work explored whether such build­ing blocks can be com­prised of only the 10 pre­bi­otic amino acids and still fold. Blaber’s team has achieved fold­abil­ity in pro­teins down to 12 amino acids — about 80 per­cent of the way to prov­ing his hypothesis.

If Blaber’s the­ory holds, sci­en­tists may refo­cus where they look for evi­dence in the quest to under­stand where, and how, life began.

“Rather than a curi­ous niche that life evolved into, the halophile envi­ron­ment now may take cen­ter stage as the likely loca­tion for key aspects of abio­gen­e­sis,” he said. “Like­wise, the role of the for­ma­tion of pro­teins takes on addi­tional impor­tance in the ear­li­est steps in the begin­nings of life on Earth.”


The above news item is reprinted from mate­ri­als avail­able at Florida State Uni­ver­sity. Orig­i­nal text may be edited for con­tent and length.
(Source: Florida State Uni­ver­sity news, 05.04.2013)

UN Biodiversity decade
WWF Stop Wildlife Crime
Fight for Flight campaign
End Ivory-funded Terrorism
Support Rewilding Europe
NASA State of Flux

Goal: 7000 tigers in the wild

Tiger range countries map

Tiger map” (CC BY 2.5) by Sander­son et al., 2006.

about zoos and their mis­sion regard­ing breed­ing endan­gered species, nature con­ser­va­tion, bio­di­ver­sity and edu­ca­tion, which of course relates to the evo­lu­tion of species.
Fol­low me on: