Browsing by Subject "Molecular Motor Proteins"
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Item Open Access Evidence for an electrostatic mechanism of force generation by the bacteriophage T4 DNA packaging motor.(Nat Commun, 2014-06-17) Migliori, Amy D; Keller, Nicholas; Alam, Tanfis I; Mahalingam, Marthandan; Rao, Venigalla B; Arya, Gaurav; Smith, Douglas EHow viral packaging motors generate enormous forces to translocate DNA into viral capsids remains unknown. Recent structural studies of the bacteriophage T4 packaging motor have led to a proposed mechanism wherein the gp17 motor protein translocates DNA by transitioning between extended and compact states, orchestrated by electrostatic interactions between complimentarily charged residues across the interface between the N- and C-terminal subdomains. Here we show that site-directed alterations in these residues cause force dependent impairments of motor function including lower translocation velocity, lower stall force and higher frequency of pauses and slips. We further show that the measured impairments correlate with computed changes in free-energy differences between the two states. These findings support the proposed structural mechanism and further suggest an energy landscape model of motor activity that couples the free-energy profile of motor conformational states with that of the ATP hydrolysis cycle.Item Open Access In vivo Modeling Implicates APOL1 in Nephropathy: Evidence for Dominant Negative Effects and Epistasis under Anemic Stress.(PLoS Genet, 2015-07) Anderson, Blair R; Howell, David N; Soldano, Karen; Garrett, Melanie E; Katsanis, Nicholas; Telen, Marilyn J; Davis, Erica E; Ashley-Koch, Allison EAfrican Americans have a disproportionate risk for developing nephropathy. This disparity has been attributed to coding variants (G1 and G2) in apolipoprotein L1 (APOL1); however, there is little functional evidence supporting the role of this protein in renal function. Here, we combined genetics and in vivo modeling to examine the role of apol1 in glomerular development and pronephric filtration and to test the pathogenic potential of APOL1 G1 and G2. Translational suppression or CRISPR/Cas9 genome editing of apol1 in zebrafish embryos results in podocyte loss and glomerular filtration defects. Complementation of apol1 morphants with wild-type human APOL1 mRNA rescues these defects. However, the APOL1 G1 risk allele does not ameliorate defects caused by apol1 suppression and the pathogenicity is conferred by the cis effect of both individual variants of the G1 risk haplotype (I384M/S342G). In vivo complementation studies of the G2 risk allele also indicate that the variant is deleterious to protein function. Moreover, APOL1 G2, but not G1, expression alone promotes developmental kidney defects, suggesting a possible dominant-negative effect of the altered protein. In sickle cell disease (SCD) patients, we reported previously a genetic interaction between APOL1 and MYH9. Testing this interaction in vivo by co-suppressing both transcripts yielded no additive effects. However, upon genetic or chemical induction of anemia, we observed a significantly exacerbated nephropathy phenotype. Furthermore, concordant with the genetic interaction observed in SCD patients, APOL1 G2 reduces myh9 expression in vivo, suggesting a possible interaction between the altered APOL1 and myh9. Our data indicate a critical role for APOL1 in renal function that is compromised by nephropathy-risk encoding variants. Moreover, our interaction studies indicate that the MYH9 locus is also relevant to the phenotype in a stressed microenvironment and suggest that consideration of the context-dependent functions of both proteins will be required to develop therapeutic paradigms.Item Open Access Kinesins at a glance.(J Cell Sci, 2010-10-15) Endow, Sharyn A; Kull, F Jon; Liu, HongleiItem Open Access Report of a young girl with MYH9 mutation and review of the literature.(Journal of pediatric hematology/oncology, 2012-10) Landi, Daniel; Lockhart, Evelyn; Miller, Sara E; Datto, Michael; Rehder, Catherine; Kanaly, Angela; Thornburg, Courtney DMYH9 mutations cause the inherited macro-thrombocytopenic syndromes of May-Hegglin anomaly, Fechtner syndrome, Sebastian syndrome, and Epstein syndrome, collectively referred to as MYH9-related disease. We present the case of a girl with MYH9-related disease whose diagnosis was facilitated by platelet electron microscopy and MYH9 sequencing. We discuss our patient's clinical presentation, now with 12 years of follow-up. We also discuss management and her possible prognosis given her specific MYH9 mutation.