Agriculture Reference
In-Depth Information
sis and high-throughput screening for thermostability-improving mutations, functional
screening or comparison of homologous proteins. Some proteins have been successfully sta‐
bilized by the introduction of structural elements from thermophilic and hyperthermophilic
homologues [65]. However, the mechanisms underlying thermostability are diverse. Much
research has been focused on understanding the stabilization of the hydrophobic core and
internal structural elements of proteins [66, 67]. Recent research has also revealed that pro‐
tein surfaces have a strong influence on stability and, therefore, have to be taken into consid‐
eration. Surface residues are generally more flexible and the protein surface structure is less
motional restricted than the compact core. Mutations in the protein surface are therefore
supposed to largely affect protein stability and can be introduced to enhance protein stabili‐
ty. Much attention is paid to protein surface salt bridges, as it is known that surface salt
bridges become more favorable with increasing temperature and hyperthermophilic pro‐
teins tend to have more salt bridges than their mesophilic homologues. Emphasis is made to
investigate the contribution of surface salt bridges to enhanced protein stability under stress
conditions.
Information from the protein biochemistry field will direct us toward an understanding of
the rules for protein folding stability and dynamics with the goal to improve protein stabili‐
ty and stress tolerance in plants.
6. Conclusion
Abiotic stresses like desiccation, flooding, high salinity or extreme temperatures are com‐
mon threats to plants and the optimal function of their metabolism. Protein conformation
and stability is dramatically affected by sudden changes in the environment, giving rise to
protein unfolding, misfolding and aggregation. Finding the rules for protein folding and un‐
folding that lead to conformational stability is a matter of ongoing research. Folded states
represent the most stable forms under native conditions, but partially folded states that al‐
low for efficient interaction with binding partners are of fundamental importance in biologi‐
cal activity. Studying protein stability under stress conditions has to take protein dynamics,
meaning conformational changes of proteins with time, into consideration. Advances have
been made in methods to study the conformational exchange in proteins and their folding
stability under varying experimental conditions. Nuclear magnetic resonance spectroscopy
techniques have been introduced to study the interconversion between folded and partially
folded intermediate states. These short-lived, partially folded, states are extremely impor‐
tant for biological activity and play a major role in the energy landscape of proteins. NMR
relaxation dispersion experiments revealed that such low populated intermediate folding
states are strongly affected by solvent and co-solvent conditions. One of the early onsets of
the stress response in plants is the accumulation of osmolytes that serve for osmotic adjust‐
ment and protect proteins by maintaining water at the protein surface where it is most need‐
ed. NMR dynamic measurements revealed that addition of osmolytes ( myo -Inositol, pinitol,
quebrachitol and quercitol) lead to a decreased population of the partially folded state by
shifting the folding equilibrium towards the folded ensembles. Although osmolytes do not
Search WWH ::




Custom Search