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Proteins assemble into complexes with diverse quaternary structures. Although most heteromeric complexes of known structure have even stoichiometry, a significant minority have uneven stoichiometry—that is, differing numbers of each subunit type. To adopt this uneven stoichiometry, sequence-identical subunits must be asymmetric with respect to each other, forming different interactions within the complex. Here we first investigate the occurrence of uneven stoichiometry, demonstrating that it is common in vitro and is likely to be common in vivo. Next, we elucidate the structural determinants of uneven stoichiometry, identifying six different mechanisms by which it can be achieved. Finally, we study the frequency of uneven stoichiometry across evolution, observing a significant enrichment in bacteria compared with eukaryotes. We show that this arises due to a general increased tendency for bacterial proteins to self-assemble and form homomeric interactions, even within the context of a heteromeric complex.
Interactions between proteins often result in their assembly into complexes with defined quaternary structure topologies. Given that protein complexes are essential to most biological processes, there is a clear need to understand the principles by which assembly occurs and quaternary structure is organized. Although proteomic analyses have provided tremendous insights into the subunit compositions of protein complexes,,, most of the deep insight into protein complex assembly and quaternary structure has come from detailed structural investigations. We now have experimental data on the assembly, structure, dynamics and function of a wide range of protein complexes, ranging from small complexes such as haemoglobin, to large macromolecular machines such as the proteasome. Furthermore, structure-based protein complex design has become feasible in certain cases. Finally, structural bioinformatic approaches combined with mass spectrometry have revealed that most complexes assemble via ordered pathways that are generally conserved, and that show striking similarities to their evolutionary pathways.
Bosch Dishwasher Sgs65m08au Manual Lawn more. Symmetry is a key feature of many protein complexes. Most homomeric complexes (that is, those containing only a single type of subunit) and many heteromeric complexes (that is, those with multiple distinct subunits) are symmetric and can be classified into a limited number of closed symmetry groups.
Mar 16, 2015. Although most heteromeric complexes of known structure have even stoichiometry, a significant minority have uneven stoichiometry—that is, differing numbers. Interactions between proteins often result in their assembly into complexes with defined quaternary structure topologies. Protein Structure Prediction, Sequence Analysis and Protein Folding. 10.1 Introduction. 102 Some Basic Principles of Protein Structure. 10.3 First-principles Methods for Predicting Protein Structure. 10.4 Introduction to Comparative Modelling. 10.5 Sequence Alignment. 10.6 Constructing and Evaluating a Comparative.
Naruto Generations Keygen Download For Mac there. Despite this preponderance of symmetry in crystallized protein complexes, asymmetry is also common and often important. Although many complexes can be classified into closed symmetry groups, there are often small-to-moderate conformational differences observed between sequence-identical subunits within the same ‘symmetric’ homomer. Furthermore, any heteromer that has uneven subunit stoichiometry (that is, 2:1 or 3:1) will inherently have some degree of asymmetry.
This is because, to assemble a complex with uneven stoichiometry, different subunits of the same type must necessarily exist in different local environments. This can be seen in, where complexes with even and uneven stoichiometry are shown. For the complex with uneven 2:1 stoichiometry, the single low stoichiometry (L) subunit binds two high stoichiometry (H) subunits through different surfaces.
As each H subunit interacts with a different region on the L subunit, they are in non-equivalent positions within the complex. Several well known complexes have uneven stoichiometry. The mechanisms by which this asymmetric uneven stoichiometry can been formed have been discussed for some specific cases. In general, however, little attention has been paid to the differences between complexes with even or uneven stoichiometry, and there has been no systematic analysis of the phenomenon. Here, we perform a detailed investigation into protein complexes with uneven stoichiometry. We find that uneven stoichiometry is common in heteromeric complexes and that there is likely to be a strong tendency for the uneven stoichiometry observed crystallographically to also be present in vivo. We then illustrate how uneven stoichiometry can be facilitated by diverse structural mechanisms.