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Objectives Our study aims to identify genetic variants associated with hereditary gingival fibromatosis (HGF) by applying whole exome sequencing (WES) and bioinformatics analyses such as gene set enrichment analysis (GSEA) and protein functional network study. Subjects and Methods Two affected siblings whose grandparents and parents have normal gingiva were chosen for our investigation. Saliva collected from the patients and their parents were used for WES. GSEA and protein functional network study were performed to find gene groups in a biological coordination which are associated with HGF. Results Genetic variants for homozygotes and compound heterozygotes were analyzed and translated into 845 genes. The result from protein functional network study showed that these genetic variants were mainly observed in genes affecting fibronectin as well as the immune and auto-immune system. Additionally, three mutated genes in our HGF patients, TMCO1, RIN2, and INSR,were found through human phenotype ontology (HPO) to have potential to contribute to gingival hyperplasia. Conclusions Genetic analysis of HGF in this study implicated mutations in fibronectin and the immune system as triggering abnormal gingival fibromatosis. This article is protected by copyright. All rights reserved.

The evolutionary adaptations of thermophilic water-soluble proteins required for maintaining stability at high temperature have been extensively investigated. Little is known about the adaptations in membrane proteins, however. Here, we compare many properties of mesophilic and thermophilic membrane protein structures, including side-chain burial, packing, hydrogen bonding, transmembrane kinks, loop lengths, hydrophobicity, and other sequence features. Most of these properties are quite similar between mesophiles and thermophiles although we observe a slight increase in side-chain burial and possibly a slight decrease in the frequency of transmembrane kinks in thermophilic membrane protein structures. The most striking difference is the increased hydrophobicity of thermophilic transmembrane helices, possibly reflecting more stringent hydrophobicity requirements for membrane partitioning at high temperature. In agreement with prior work examining transmembrane sequences, we find that thermophiles have an increase in small residues (Gly, Ala, Ser, and Val) and a strong suppression of Cys. We also find a relative dearth of most strongly polar residues (Asp, Asn, Glu, Gln, and Arg). These results suggest that in thermophiles, there is significant evolutionary pressure to offload destabilizing polar amino acids, to decrease the entropy cost of side chain burial, and to eliminate thermally sensitive amino acids.

Protein interfaces are believed to be evolutionarily more conserved than the rest of the protein surface, but this has not been properly verified using a large protein structural set. Furthermore, recent systematic protein interaction analyses have proved that proteins interacting with many partners have multiple interfaces to connect protein interaction networks, which have never taken into account for conservation analysis of protein interface. Here, we studied the evolutionary conservation of protein interfaces using a large-scale dataset of 2646 protein interfaces with the classification of homodimeric/heterodimeric and obligatory/transient interactions, considering all their known multiple interfaces. We found that protein interfaces were indeed more conserved than noninterface surfaces, and the conservation level of protein interfaces increased when multiple interfaces were properly considered. These findings suggest that conservation analysis should be a good descriptor for protein interface identification and protein-protein interaction predictions. We applied this evolutionary feature to filter docking decoys and found that protein interface conservation worked remarkably well in selecting the near-native structures from the large number of generated docking complexes. Moreover, we discovered that a strong correlation exist between protein interface size and protein interface conservation, which could be a useful filter for the prediction of protein-protein interactions.

Symmetry plays significant roles in protein structure and function. Particularly, symmetric interfaces are known to act as switches for two-state conformational change. Membrane proteins often undergo two-state conformational change during the transport process of ion channels or the active/inactive transitions in receptors. Here, we provide the first comprehensive analyses of internal repeat symmetry in membrane proteins. We examined the known membrane protein structures and found that, remarkably, nearly half of them have internal repeat symmetry. Moreover, we found that the conserved cores of these internal repeats are positioned at the interface of symmetric units when they are mapped on structures. Because of the large sequence divergence that occurs between internal repeats, the inherent symmetry present in protein sequences often has only been detected after structure determination. We therefore developed a sensitive procedure to predict the internal repeat symmetry from sequence information and identified 4653 proteins that are likely to have internal repeat symmetry. Proteins 2008. © 2007 Wiley-Liss, Inc.

One of the goals of structural genomics is to obtain a structural representative of almost every fold in nature. A recent estimate suggests that 70%-80% of soluble protein domains identified in the first 1000 genome sequences should be covered by about 25,000 structures-a reasonably achievable goal. As no current estimates exist for the number of membrane protein families, however, it is not possible to know whether family coverage is a realistic goal for membrane proteins. Here we find that virtually all polytopic helical membrane protein families are present in the already known sequences so we can make an estimate of the total number of families. We find that only approximately 700 polytopic membrane protein families account for 80% of structured residues and approximately 1700 cover 90% of structured residues. While apparently a finite and reachable goal, we estimate that it will likely take more than three decades to obtain the structures needed for 90% residue coverage, if current trends continue.