Researchers Tackling Unsolved Questions About Protein Structures

May 07, 2008
Researchers Tackling Unsolved Questions About Protein Structures
Two protein structures.

A University of Arizona research team is exploring the evolutionary origins of protein structures. Their findings will help people better understand how proteins evolved to carry out the instructions encoded in the genes of every living thing.

Protein molecules are made up of chains of amino acids. These chains bend and fold into a dizzying array of three-dimensional shapes and structures, depending on the order of the amino acids in a given chain. Those varied structures are part of what allow the proteins – which are assembled based on instructions coded in DNA – to regulate everything from an organism's growth and metabolism to the ways messages are transmitted from cell to cell. Protein structures are at the heart of how organisms function.

However, the evolution of those structures is still poorly understood, because there are few observed examples of proteins that have clearly evolved from one shape to another.

"The origin of the diversity of protein structures is a major unsolved problem," explains Matthew H.J. Cordes, a member of the UA's BIO5 Institute and an associate professor of biochemistry and molecular biophysics.

Cordes' lab is solving that problem. Two graduate students in his lab, Christian M. Roessler and Branwen M. Hall, have located protein molecules in two different viruses that have dramatically different structures: One protein has a helical, or corkscrew, shape, while the other is shaped more like a hairpin. Yet these very different proteins have similar amino acid sequences and perform similar functions – binding to DNA to help the viruses replicate and spread – making it likely that they had a common ancestor.

"Somehow, mutations converted the corkscrew structure to the hairpin structure," Cordes says of the finding, which was recently reported in the Proceedings of the National Academy of Sciences.

While this isn't the first example of structural differences among proteins with a common ancestor, it may be the most dramatic natural example of related proteins retaining clear similarity in amino acid sequence while undergoing major reorganization of their structure.

"This finding strongly confirms that evolutionary processes produce new protein shapes," Cordes says. "It could become a textbook example of the reality and beauty of evolutionary changes in structure." He adds that some proteins in this family with the hairpin shape bind to DNA more strongly than those with the corkscrew shape, though it is too early to tell if this is always the case. It's not yet known whether such an advantage helped drive the hairpin structure's evolution.

Cordes' graduate students found their protein pair via an unusual method: Roessler and Hall used a stepping-stone technique to make a series of small "jumps" among closely related proteins, following minute structural changes from one protein to another until they "landed" at a protein that was dramatically different from the one they'd started with, yet was still related to it.

Cordes' lab is now working out the details of the specific mutations that might have caused their two proteins to diverge from one another. They also plan to use their stepping-stone technique to shed light on the evolutionary links among other proteins.

"This is like space exploration," Cordes says. "We're journeying through the protein universe, step by step."

Source: University of Arizona

Explore further: New conversion process turns biomass 'waste' into lucrative chemical products (w/ Video)

add to favorites email to friend print save as pdf

Related Stories

Washington takes on Uber with its own taxi app

8 hours ago

Washington is developing a smartphone app to enable its taxis to compete head-on with Uber and other ride-sharing services, the US capital's taxi commission said Friday.

Comet 67P/Churyumov-Gerasimenko in living color

8 hours ago

Rosetta's OSIRIS team have produced a color image of Comet 67P/Churyumov-Gerasimenko as it would be seen by the human eye. As anticipated, the comet turns out to be very grey indeed, with only slight, subtle ...

EU clean air, waste laws at risk

8 hours ago

EU Commission chief Jean-Claude Juncker faces a clash with lawmakers after leaked documents Friday revealed his plans to drop laws on clean air and waste recycling.

Recommended for you

Protections blocked, but sage grouse work goes on

13 hours ago

(AP)—U.S. wildlife officials will decide next year whether a wide-ranging Western bird species needs protections even though Congress has blocked such protections from taking effect, Interior Secretary ...

Contrasting views of kin selection assessed

15 hours ago

In an article to be published in the January issue of BioScience, two philosophers tackle one of the most divisive arguments in modern biology: the value of the theory of "kin selection."

User comments : 1

Adjust slider to filter visible comments by rank

Display comments: newest first

E_L_Earnhardt
not rated yet May 07, 2008
You are about to solve the mystery of LIFE! Proceed with respect and caution!

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.