Three-dimensional structural analysis of calcium-dependent target recognition by calmodulin.
Published: 2004
Language: eng
Number of pages: 208
Description: Using a quantitative approach to analyze all occurrences of EF-hands in solved, high-resolution structures, it is shown that subfamilies of EF-hand proteins exhibit similar conformational patterns, yet a micro-diversity is still observed, demonstrating that EF-hand conformation is highly dependent on the overall structure, specific function and binding partners of the protein. Collation and classification of the vast amount of data available for various CaM targets enabled the design of a computational algorithm to predict CaM binding domains in a given sequence, which proved successful in identifying motifs of the basic, amphiphilic alpha-helix type, but not for unusual targets such as plant glutamate decarboxylase (GAD). To better understand the mechanisms governing these atypical interactions, the structure of CaM bound to the C-terminal domain of GAD was solved by nuclear magnetic resonance spectroscopy, revealing a pseudo-symmetric, compact complex and an unusual CaM domain-domain orientation.Many eukaryotic proteins that mediate the intracellular calcium (Ca2+) signal contain multiple copies of the Ca2+-binding,  helix-loop-helix EF-hand motif, which can undergo a conformational change upon binding Ca2+ and effect subsequent target binding and activation. While most EF-hand proteins have few binding partners, the prototypical EF-hand protein calmodulin (CaM) can specifically bind and activate hundreds of structurally and functionally diverse targets. The recognition sequences of these targets have also proved to be diverse, containing no clearly dominant consensus motif. It is astonishing, yet not well understood, how CaM can recognize so many targets, and why no other EF-hand protein exhibits this characteristic. The work described here probes the structural basis for this diversity in response to the Ca2+ signal, by examining patterns of conformational change and target recognition.These studies emphasize that for many Ca2+ binding proteins, structural diversity is dictated by the ability of the protein to adapt to specific targets and circumstances. For the EF-hand protein superfamily, variations on a motif have enabled the evolution of a multitude of specific sensors that mediate the Ca2+ signal. For CaM, certain features endowing remarkable structural flexibility have proven to be essential to its multiple targeting ability.
Notes: Adviser: Mitsuhiko Ikura.

Thesis (Ph.D.)--University of Toronto, 2004.

Electronic version licensed for access by U. of T. users.

Source: Dissertation Abstracts International, Volume: 65-10, Section: B, page: 5032.