Suryani Lukman

Computational methods for Traditional Chinese Medicine: A survey

Traditional Chinese Medicine (TCM) has been actively researched through various approaches, including computational techniques. A review on basic elements of TCM is provided to illuminate various challenges and progresses in its study using computational methods. Information on various TCM formulations, in particular resources on databases of TCM formulations and their integration to Western medicine, are analyzed in several facets, such as TCM classifications, types of databases, and mining tools. Aspects of computational TCM diagnosis, namely inspection, auscultation, pulse analysis as well as TCM expert systems are reviewed in term of their benefits and drawbacks. Various approaches on exploring relationships among TCM components and finding genes/proteins relating to TCM symptom complex are also studied. This survey provides a summary on the advance of computational approaches for TCM and will be useful for future knowledge discovery in this area.

Novel allosteric sites on ras for lead generation

Aberrant Ras activity is a hallmark of diverse cancers and developmental diseases. Unfortunately, conventional efforts to develop effective small molecule Ras inhibitors have met with limited success. We have developed a novel multi-level computational approach to discover potential inhibitors of previously uncharacterized allosteric sites. Our approach couples bioinformatics analysis, advanced molecular simulations, ensemble docking and initial experimental testing of potential inhibitors. Molecular dynamics simulation highlighted conserved allosteric coupling of the nucleotide-binding switch region with distal regions, including loop 7 and helix 5. Bioinformatics methods identified novel transient small molecule binding pockets close to these regions and in the vicinity of the conformationally responsive switch region. Candidate binders for these pockets were selected through ensemble docking of ZINC and NCI compound libraries. Finally, cell-based assays confirmed our hypothesis that the chosen binders can inhibit the downstream signaling activity of Ras. We thus propose that the predicted allosteric sites are viable targets for the development and optimization of new drugs.

The Distinct Conformational Dynamics of K-Ras and H-Ras A59G

Ras proteins regulate signaling cascades crucial for cell proliferation and differentiation by switching between GTP- and GDP-bound conformations. Distinct Ras isoforms have unique physiological functions with individual isoforms associated with different cancers and developmental diseases. Given the small structural differences among isoforms and mutants, it is currently unclear how these functional differences and aberrant properties arise. Here we investigate whether the subtle differences among isoforms and mutants are associated with detectable dynamical differences. Extensive molecular dynamics simulations reveal that wild-type K-Ras and mutant H-Ras A59G are intrinsically more dynamic than wild-type H-Ras. The crucial switch 1 and switch 2 regions along with loop 3, helix 3, and loop 7 contribute to this enhanced flexibility. Removing the gamma-phosphate of the bound GTP from the structure of A59G led to a spontaneous GTP-to-GDP conformational transition in a 20-ns unbiased simulation. The switch 1 and 2 regions exhibit enhanced flexibility and correlated motion when compared to non-transitioning wild-type H-Ras over a similar timeframe. Correlated motions between loop 3 and helix 5 of wild-type H-Ras are absent in the mutant A59G reflecting the enhanced dynamics of the loop 3 region. Taken together with earlier findings, these results suggest the existence of a lower energetic barrier between GTP and GDP states of the mutant. Molecular dynamics simulations combined with principal component analysis of available Ras crystallographic structures can be used to discriminate ligand- and sequence-based dynamic perturbations with potential functional implications. Furthermore, the identification of specific conformations associated with distinct Ras isoforms and mutants provides useful information for efforts that attempt to selectively interfere with the aberrant functions of these species.

Mapping the Structural and Dynamical Features of Multiple p53 DNA Binding Domains: Insights into Loop 1 Intrinsic Dynamics

The transcription factor p53 regulates cellular integrity in response to stress. p53 is mutated in more than half of cancerous cells, with a majority of the mutations localized to the DNA binding domain (DBD). In order to map the structural and dynamical features of the DBD, we carried out multiple copy molecular dynamics simulations (totaling 0.8 μs). Simulations show the loop 1 to be the most dynamic element among the DNA-contacting loops (loops 1-3). Loop 1 occupies two major conformational states: extended and recessed; the former but not the latter displays correlations in atomic fluctuations with those of loop 2 (~24 Å apart). Since loop 1 binds to the major groove whereas loop 2 binds to the minor groove of DNA, our results begin to provide some insight into the possible mechanism underpinning the cooperative nature of DBD binding to DNA. We propose (1) a novel mechanism underlying the dynamics of loop 1 and the possible tread-milling of p53 on DNA and (2) possible mutations on loop 1 residues to restore the transcriptional activity of an oncogenic mutation at a distant site.

Centroid-Based Actionable 3D Subspace Clustering

Actionable 3D subspace clustering from real-world continuous-valued 3D (i.e., object-attribute-context) data promises tangible benefits such as discovery of biologically significant protein residues and profitable stocks, but existing algorithms are inadequate in solving this clustering problem; most of them are not actionable (ability to suggest profitable or beneficial actions to users), do not allow incorporation of domain knowledge, and are parameter sensitive, i.e., the wrong threshold setting reduces the cluster quality. Moreover, its 3D structure complicates this clustering problem. We propose a centroid-based actionable 3D subspace clustering framework, named CATSeeker, which allows incorporation of domain knowledge, and achieves parameter insensitivity and excellent performance through a unique combination of singular value decomposition, numerical optimization, and 3D frequent itemset mining. Experimental results on synthetic, protein structural, and financial data show that CATSeeker significantly outperforms all the competing methods in terms of efficiency, parameter insensitivity, and cluster usefulness.

Unraveling evolutionary constraints: a heterogeneous conservation in dynamics of the titin Ig domains.

The giant protein titin, which comprises immunoglobulin (Ig) domains, acts as a bidirectional spring in muscle. The unfolding of Ig domains has been extensively studied, but their dynamics under native states have not been well‐characterized. We performed molecular dynamics simulation on a single titin Ig domain and multi‐domains. Mobile regions displaying concerted motions were identified. The dynamics of Ig domains are constrained by evolutionary pressures, in such a way that global dominant motion is conserved, yet different flexibilities within Ig domains and in linkers connecting neighbouring domains were observed. We explain these heterogeneous conserved dynamics in relation to sequence conservation across species and the sequence diversity among neighbouring Ig domains.

A network of dynamically conserved residues deciphers the motions of maltose transporter.

The maltose transporter of Escherichia coli is a member of the ATP‐binding cassette (ABC) transporter superfamily. The crystal structures of maltose transporter MalK have been determined for distinct conformations in the presence and absence of the ligand ATP, and other interacting proteins. Using the distinct MalK structures, normal mode analysis was performed to understand the dynamics behavior of the system. A network of dynamically important residues was obtained from the normal mode analysis and the analysis of point mutation on the normal modes. Our results suggest that the intradomain rotation occurs earlier than the interdomain rotation during the maltose‐binding protein (MBP)‐driven conformational changes of MalK. We inquire if protein motion and functional‐driven evolutionary conservation are related. The sequence conservation of MalK was analyzed to derive a network of evolutionarily important residues. There are highly significant correlations between protein sequence and protein dynamics in many regions on the maltose transporter MalK, suggesting a link between the protein evolution and dynamics. The significant overlaps between the network of dynamically important residues and the network of evolutionarily important residues form a network of dynamically conserved residues. Proteins 2009.

Conformational dynamics of capping protein and interaction partners: Simulation studies

Capping protein (CP) is important for the regulation of actin polymerization. CP binds to the barbed end of the actin filament and prevents actin polymerization. This interaction is modulated through competitive binding by regulatory proteins such as myotrophin (V‐1) and the capping protein interacting (CPI) motif from CARMIL. The binding site of myotrophin overlaps with the region of CP that binds to the barbed end of actin filament, whereas CPI binds at a distant site. The binding of CPI to the myotrophin‐CP complex dissociates myotrophin from CP. Detailed multicopy molecular dynamics simulations suggest that the binding of CPI shifts the conformational equilibria of CP away from states that favor myotrophin binding. This shift is underpinned by allosteric effects where CPI inhibits CP through suppression of flexibility and disruption of concerted motions that appear to mediate myotrophin binding. Accompanying these effects are changes in electrostatic interactions, notably those involving residue K142β, which appears to play a critical role in regulating flexibility. In addition, accessibility of the site on CP for binding the key hydrophobic residue W8 of myotrophin is modulated by CPI. These results provide insights into the modulation of CP by CPI and myotrophin and indicate the mechanism by which CPI drives the dissociation of the myotrophin‐CP complex. Proteins 2012;.

Interacting amino acid preferences of 3D pattern pairs at the binding sites of transient and obligate protein complexes

To assess the physico-chemical characteristics of protein-protein interactions, protein sequences and overall structural folds have been analyzed previously. To highlight this, discovery and examination of amino acid patterns at the binding sites defined by structural proximity in 3-dimensional (3D) space are essential. In this paper, we investigate the interacting preferences of 3D pattern pairs discovered separately in transient and obligate protein complexes. These 3D pattern pairs are not necessarily sequence-consecutive, but each residue in two groups of amino acids from two proteins in a complex is within certain °A threshold to most residues in the other group. We develop an algorithm called AA-pairs by which every pair of interacting proteins is represented as a bipartite graph, and it discovers all maximal quasi-bicliques from every bipartite graph to form our 3D pattern pairs. From 112 and 2533 highly conserved 3D pattern pairs discovered in the transient and obligate complexes respectively, we observe that Ala and Leu is the highest occuring amino acid in interacting 3D patterns of transient (20.91%) and obligate (33.82%) complexes respectively. From the study on the dipeptide composition on each side of interacting 3D pattern pairs, dipeptides Ala-Ala and Ala-Leu are popular in 3D patterns of both transient and obligate complexes. The interactions between amino acids with large hydrophobicity difference are present more in the transient than in the obligate complexes. On contrary, in obligate complexes, interactions between hydrophobic residues account for the top 5 most occuring amino acid pairings.

Multiple Structural Clustering of Bromodomains of the Bromo and Extra Terminal (BET) Proteins Highlights Subtle Differences in Their Structural Dynamics and Acetylated Leucine Binding Pocket

Abstract BET proteins are epigenetic readers whose deregulation results in cancer and inflammation. We show that BET proteins (BRD2, BRD3, BRD4 and BRDT) are globally similar with subtle differences in the sequences and structures of their N-terminal bromodomain. Principal component analysis and non-negative matrix factorization reveal distinct structural clusters associated with specific BET family members, experimental methods, and source organisms. Subtle variations in structural dynamics are evident in the acetylated lysine (Kac) binding pocket of BET bromodomains. Using multiple structural clustering methods, we have also identified representative structures of BET proteins, which are potentially useful for developing potential therapeutic agents.