Quality of life in young adults with acne: Results of a cross-sectional study.

BACKGROUND: The impact of acne on quality of life (QoL) may vary between patients from different age groups. There are limited data in the literature on QoL of young adults with acne and acne scars. OBJECTIVES: To assess the QoL of young adults (age 18 to 25) with acne by using dermatology life quality index (DLQI) and Cardiff acne disability index (CADI), to assess the scores of individual items on DLQI and CADI, and to compare the two scales. METHODS: In this cross-sectional questionnaire study of 1392 subjects with acne, each subject completed two questionnaires: DLQI and CADI. Mean values of DLQI and CADI, and those of individual items on DLQI and CADI were calculated; t-test was used for testing mean values and Spearman's rho coefficient for correlation between two questionnaires. RESULTS: Mean DLQI (4.50) and CADI (3.60) scores were low. However, scores were significantly higher in females and in those with acne scars. "Feelings of embarrassment" and "interference with social activities" scored significantly higher for females across both questionnaires. There was no correlation between severity (as well as duration) of acne and HRQoL scores. Spearman's rho coefficient of correlation between DLQI and CADI was 0.71. CONCLUSIONS: Acne impaired the QoL of young adults, acne scars more so. Females felt worse about their appearance with greater embarrassment and impaired social activities. QoL scores seem to depend on patients' perceptions, which may depend on factors other than objective severity of acne. We found good correlation between the two scales.

Cell-free Generation of COPII-coated Procollagen I Carriers.

The aim of this protocol is to generate COPII-coated procollagen I (PC1) carriers in a cell-free reaction. The COPII-coated PC1 carriers were reconstituted from donor membrane, cytosol, purified recombinant COPII proteins, and nucleotides. This protocol describes the preparation of donor membrane and cytosol, the assembly of the reaction, and the isolation and detection of reconstituted COPII-coated carriers. This cell-free reaction can be used to test conditions that stimulate or suppress the packaging of PC1 into COPII-coated carriers.

SEC24A deficiency lowers plasma cholesterol through reduced PCSK9 secretion.

The secretory pathway of eukaryotic cells packages cargo proteins into COPII-coated vesicles for transport from the endoplasmic reticulum (ER) to the Golgi. We now report that complete genetic deficiency for the COPII component SEC24A is compatible with normal survival and development in the mouse, despite the fundamental role of SEC24 in COPII vesicle formation and cargo recruitment. However, these animals exhibit markedly reduced plasma cholesterol, with mutations in Apoe and Ldlr epistatic to Sec24a, suggesting a receptor-mediated lipoprotein clearance mechanism. Consistent with these data, hepatic LDLR levels are up-regulated in SEC24A-deficient cells as a consequence of specific dependence of PCSK9, a negative regulator of LDLR, on SEC24A for efficient exit from the ER. Our findings also identify partial overlap in cargo selectivity between SEC24A and SEC24B, suggesting a previously unappreciated heterogeneity in the recruitment of secretory proteins to the COPII vesicles that extends to soluble as well as trans-membrane cargoes. DOI:http://dx.doi.org/10.7554/eLife.00444.001.

Protein model discrimination using mutational sensitivity derived from deep sequencing.

A major bottleneck in protein structure prediction is the selection of correct models from a pool of decoys. Relative activities of ∼1,200 individual single-site mutants in a saturation library of the bacterial toxin CcdB were estimated by determining their relative populations using deep sequencing. This phenotypic information was used to define an empirical score for each residue (RankScore), which correlated with the residue depth, and identify active-site residues. Using these correlations, ∼98% of correct models of CcdB (RMSD ≤ 4Å) were identified from a large set of decoys. The model-discrimination methodology was further validated on eleven different monomeric proteins using simulated RankScore values. The methodology is also a rapid, accurate way to obtain relative activities of each mutant in a large pool and derive sequence-structure-function relationships without protein isolation or characterization. It can be applied to any system in which mutational effects can be monitored by a phenotypic readout.

Structural correlates of the temperature sensitive phenotype derived from saturation mutagenesis studies of CcdB.

Temperature sensitive (ts) mutants are widely used to reversibly modulate protein function in vivo and to understand functions of essential genes. Despite this, little is known about the protein structural features and mechanisms responsible for generating a ts phenotype. Also, such mutants are often difficult to isolate, limiting their use. In this study, a library consisting of 75% of all possible single-site mutants of the 101-residue, homodimeric Escherichia coli toxin CcdB was constructed. Mutants were characterized in terms of their activity at two different temperatures and at six different expression levels. Of the total of 1430 single-site mutants that were screened, 231 (16%) mutants showed a ts phenotype. The bulk of these consisted of 120 ts mutants found at all 22 buried sites and 34 ts mutants at all seven active site residues involved in binding DNA gyrase. Of the remaining ts mutants, 16 were found at residues in van der Waals contact with active site residues, 36 were at partially buried residues, and 30 resulted from introduction of Pro. Thus virtually all ts mutants could be rationalized in terms of the structure of the native protein and without knowledge of folding pathways. Data were analyzed to obtain insights into molecular features responsible for the ts phenotype and to outline structure- and sequence-based criteria for designing ts mutants of any globular protein. The criteria were validated by successful prediction of ts mutants of three other unrelated proteins, TBP, T4 lysozyme, and Gal4.

Refolding and simultaneous purification by three-phase partitioning of recombinant proteins from inclusion bodies.

Many recombinant eukaryotic proteins tend to form insoluble aggregates called inclusion bodies, especially when expressed in Escherichia coli. We report the first application of the technique of three-phase partitioning (TPP) to obtain correctly refolded active proteins from solubilized inclusion bodies. TPP was used for refolding 12 different proteins overexpressed in E. coli. In each case, the protein refolded by TPP gave either higher refolding yield than the earlier reported method or succeeded where earlier efforts have failed. TPP-refolded proteins were characterized and compared to conventionally purified proteins in terms of their spectral characteristics and/or biological activity. The methodology is scaleable and parallelizable and does not require subsequent concentration steps. This approach may serve as a useful complement to existing refolding strategies of diverse proteins from inclusion bodies.

Stereochemical criteria for prediction of the effects of proline mutations on protein stability.

When incorporated into a polypeptide chain, proline (Pro) differs from all other naturally occurring amino acid residues in two important respects. The phi dihedral angle of Pro is constrained to values close to -65 degrees and Pro lacks an amide hydrogen. Consequently, mutations which result in introduction of Pro can significantly affect protein stability. In the present work, we describe a procedure to accurately predict the effect of Pro introduction on protein thermodynamic stability. Seventy-seven of the 97 non-Pro amino acid residues in the model protein, CcdB, were individually mutated to Pro, and the in vivo activity of each mutant was characterized. A decision tree to classify the mutation as perturbing or nonperturbing was created by correlating stereochemical properties of mutants to activity data. The stereochemical properties including main chain dihedral angle phi and main chain amide H-bonds (hydrogen bonds) were determined from 3D models of the mutant proteins built using MODELLER. We assessed the performance of the decision tree on a large dataset of 163 single-site Pro mutations of T4 lysozyme, 74 nsSNPs, and 52 other Pro substitutions from the literature. The overall accuracy of this algorithm was found to be 81% in the case of CcdB, 77% in the case of lysozyme, 76% in the case of nsSNPs, and 71% in the case of other Pro substitution data. The accuracy of Pro scanning mutagenesis for secondary structure assignment was also assessed and found to be at best 69%. Our prediction procedure will be useful in annotating uncharacterized nsSNPs of disease-associated proteins and for protein engineering and design.

Mutagenesis-based definitions and probes of residue burial in proteins.

Every residue of the 101-aa Escherichia coli toxin CcdB was substituted with Ala, Asp, Glu, Lys, and Arg by using site-directed mutagenesis. The activity of each mutant in vivo was characterized as a function of Controller of Cell Division or Death B protein (CcdB) transcriptional level. The mutation data suggest that an accessibility value of 5% is an appropriate cutoff for definition of buried residues. At all buried positions, introduction of Asp results in an inactive phenotype at all CcdB transcriptional levels. The average amount of destabilization upon substitution at buried positions decreases in the order Asp>Glu>Lys>Arg>Ala. Asp substitutions at buried sites in two other proteins, maltose-binding protein and thioredoxin, also were shown to be severely destabilizing. Ala and Asp scanning mutagenesis, in combination with dose-dependent expression phenotypes, was shown to yield important information on protein structure and activity. These results also suggest that such scanning mutagenesis data can be used to rank order sequence alignments and their corresponding homology models, as well as to distinguish between correct and incorrect structural alignments. With continuous reductions in oligonucleotide costs and increasingly efficient site-directed mutagenesis procedures, comprehensive scanning mutagenesis experiments for small proteins/domains are quite feasible.

Unfolding studies on soybean agglutinin and concanavalin a tetramers: a comparative account.

The unfolding pathway of two very similar tetrameric legume lectins soybean agglutinin (SBA) and Concanavalin A (ConA) were determined using GdnCl-induced denaturation. Both proteins displayed a reversible two-state unfolding mechanism. The analysis of isothermal denaturation data provided values for conformational stability of the two proteins. It was found that the DeltaG of unfolding of SBA was much higher than ConA at all the temperatures at which the experiments were done. ConA had a T(g) 18 degrees C less than SBA. The higher conformational stability of SBA in comparison to ConA is largely due to substantial differences in their degrees of subunit interactions. Ionic interactions at the interface of the two proteins especially at the noncanonical interface seem to play a significant role in the observed stability differences between these two proteins. Furthermore, SBA is a glycoprotein with a GlcNac2Man9 chain attached to Asn-75 of each subunit. The sugar chain in SBA lies at the noncanonical interface of the protein, and it is found to interact with the amino acid residues in the adjacent noncanonical interface. These interactions further stabilize SBA with respect to ConA, which is not glycosylated.

Accurate detection of protein:ligand binding sites using molecular dynamics simulations.

Accurate prediction of location of cavities and surface grooves in proteins is important, as these are potential sites for ligand binding. Several currently available programs for cavity detection are unable to detect cavities near the surface or surface grooves. In the present study, an optimized molecular dynamics based procedure is described for detection and quantification of interior cavities as well as surface pockets. This is based on the observation that the mobility of water in such pockets is significantly lower than that of bulk water. The algorithm efficiently detects surface grooves that are sites of protein-ligand and protein-protein interaction. The algorithm was also used to substantially improve the performance of an automated docking procedure for docking monomers of nonobligate protein-protein complexes. In addition, it was applied to predict key residues involved in the binding of the E. coli toxin CcdB with its inhibitor. Predictions were subsequently validated by mutagenesis experiments.

Thermodynamic characterization of monomeric and dimeric forms of CcdB (controller of cell division or death B protein).

The protein CcdB (controller of cell division or death B) is an F-plasmid-encoded toxin that acts as an inhibitor of Escherichia coli DNA gyrase. The stability and aggregation state of CcdB have been characterized as a function of pH and temperature. Size-exclusion chromatography revealed that the protein is a dimer at pH 7.0, but a monomer at pH 4.0. CD analysis and fluorescence spectroscopy showed that the monomer is well folded, and has similar tertiary structure to the dimer. Hence intersubunit interactions are not required for folding of individual subunits. The stability of both forms was characterized by isothermal denaturant unfolding and calorimetry. The free energies of unfolding were found to be 9.2 kcal x mol(-1) (1 cal approximately 4.184 J) and 21 kcal x mol(-1) at 298 K for the monomer and dimer respectively. The denaturant concentration at which one-half of the protein molecules are unfolded (C(m)) of the dimer is dependent on protein concentration, whereas the C(m) of the monomer is independent of protein concentration, as expected. Although thermal unfolding of the protein in aqueous solution is irreversible at neutral pH, it was found that thermal unfolding is reversible in the presence of GdmCl (guanidinium chloride). Differential scanning calorimetry in the presence of low concentrations of GdmCl in combination with isothermal denaturation melts as a function of temperature were used to derive the stability curve for the protein. The value of Delta C (p) (representing the change in excess heat capacity upon protein denaturation) is 2.8+/-0.2 kcal x mol(-1) x K(-1) for unfolding of dimeric CcdB, and only has a weak dependence on denaturant concentration.