scholarly journals Structures of the ApoL1 and ApoL2 N-terminal domains reveal a non-classical four-helix bundle motif

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Mark Ultsch ◽  
Michael J. Holliday ◽  
Stefan Gerhardy ◽  
Paul Moran ◽  
Suzie J. Scales ◽  
...  
Keyword(s):  
Trypanosome Infection ◽  
X Ray ◽  
Helix Bundle ◽  
Nmr Structures ◽  
Increased Risk ◽  
Functional Understanding ◽  
Four Helix Bundle ◽  
Α Helix ◽  
Coding Variants ◽  
Apolipoprotein L1

AbstractApolipoprotein L1 (ApoL1) is a circulating innate immunity protein protecting against trypanosome infection. However, two ApoL1 coding variants are associated with a highly increased risk of chronic kidney disease. Here we present X-ray and NMR structures of the N-terminal domain (NTD) of ApoL1 and of its closest relative ApoL2. In both proteins, four of the five NTD helices form a four-helix core structure which is different from the classical four-helix bundle and from the pore-forming domain of colicin A. The reactivity with a conformation-specific antibody and structural models predict that this four-helix motif is also present in the NTDs of ApoL3 and ApoL4, suggesting related functions within the small ApoL family. The long helix 5 of ApoL1 is conformationally flexible and contains the BH3-like region. This BH3-like α-helix resembles true BH3 domains only in sequence and structure but not in function, since it does not bind to the pro-survival members of the Bcl-2 family, suggesting a Bcl-2-independent role in cytotoxicity. These findings should expedite a more comprehensive structural and functional understanding of the ApoL immune protein family.

scholarly journals Structural basis for the alternating access mechanism of the cation diffusion facilitator YiiP

2018 ◽  
Vol 115 (12) ◽  
pp. 3042-3047 ◽  
Author(s):  
Maria Luisa Lopez-Redondo ◽  
Nicolas Coudray ◽  
Zhening Zhang ◽  
John Alexopoulos ◽  
David L. Stokes
Keyword(s):  
Large Scale ◽  
Structural Basis ◽  
Membrane Domains ◽  
Cation Diffusion ◽  
Cation Diffusion Facilitator ◽  
X Ray ◽  
Bacterial Membranes ◽  
Helix Bundle ◽  
Four Helix Bundle ◽  
Alternating Access

YiiP is a dimeric antiporter from the cation diffusion facilitator family that uses the proton motive force to transport Zn2+ across bacterial membranes. Previous work defined the atomic structure of an outward-facing conformation, the location of several Zn2+ binding sites, and hydrophobic residues that appear to control access to the transport sites from the cytoplasm. A low-resolution cryo-EM structure revealed changes within the membrane domain that were associated with the alternating access mechanism for transport. In the current work, the resolution of this cryo-EM structure has been extended to 4.1 Å. Comparison with the X-ray structure defines the differences between inward-facing and outward-facing conformations at an atomic level. These differences include rocking and twisting of a four-helix bundle that harbors the Zn2+ transport site and controls its accessibility within each monomer. As previously noted, membrane domains are closely associated in the dimeric structure from cryo-EM but dramatically splayed apart in the X-ray structure. Cysteine crosslinking was used to constrain these membrane domains and to show that this large-scale splaying was not necessary for transport activity. Furthermore, dimer stability was not compromised by mutagenesis of elements in the cytoplasmic domain, suggesting that the extensive interface between membrane domains is a strong determinant of dimerization. As with other secondary transporters, this interface could provide a stable scaffold for movements of the four-helix bundle that confers alternating access of these ions to opposite sides of the membrane.

Gene of the month: APOL1

2020 ◽  
Vol 73 (8) ◽  
pp. 441-443
Author(s):  
Shanel Raghubeer ◽  
Tahir S Pillay ◽  
Tandi Edith Matsha
Keyword(s):  
Systemic Lupus Erythematosus ◽  
Lupus Erythematosus ◽  
African Ancestry ◽  
Structure And Function ◽  
Trypanosome Infection ◽  
Systemic Lupus ◽  
Disease Outcomes ◽  
Increased Risk ◽  
And Function ◽  
Apolipoprotein L1

Apolipoprotein L1 (APOL1) is a protein encoded by the APOL1 gene, found only in humans and several primates. Two variants encoding two different isoforms exist for APOL1, namely G1 and G2. These variants confer increased protection against trypanosome infection, and subsequent African sleeping sickness, and also increase the likelihood of renal disease in individuals of African ancestry. APOL1 mutations are associated with increased risk of chronic kidney disease, inflammation, and exacerbation of systemic lupus erythematosus-associated renal dysfunction. This review serves to outline the structure and function of APOL1, as well as its role in several disease outcomes.

Redesign of a Four-helix Bundle Protein by Phage Display Coupled with Proteolysis and Structural Characterization by NMR and X-ray Crystallography

2002 ◽  
Vol 323 (2) ◽  
pp. 253-262 ◽  
Author(s):  
Ruiai Chu ◽  
Jiro Takei ◽  
J.Randolph Knowlton ◽  
Michelle Andrykovitch ◽  
Wuhong Pei ◽  
...  
Keyword(s):  
Phage Display ◽  
Structural Characterization ◽  
X Ray ◽  
Helix Bundle ◽  
X Ray Crystallography ◽  
Four Helix Bundle ◽  
Bundle Protein

Structure of human desArg-C5a

2010 ◽  
Vol 66 (2) ◽  
pp. 190-197 ◽  
Author(s):  
William J. Cook ◽  
Nicholas Galakatos ◽  
William C. Boyar ◽  
Richard L. Walter ◽  
Steven E. Ealick
Keyword(s):  
Disulfide Bonds ◽  
Inflammatory Diseases ◽  
Complement Cascade ◽  
Crystal Forms ◽  
Helix Bundle ◽  
Nmr Structures ◽  
Anaphylatoxin C5a ◽  
Structural Differences ◽  
Structure Determinations ◽  
Four Helix Bundle

The anaphylatoxin C5a is derived from the complement component C5 during activation of the complement cascade. It is an important component in the pathogenesis of a number of inflammatory diseases. NMR structures of human and porcine C5a have been reported; these revealed a four-helix bundle stabilized by three disulfide bonds. The crystal structure of human desArg-C5a has now been determined in two crystal forms. Surprisingly, the protein crystallizes as a dimer and each monomer in the dimer has a three-helix core instead of the four-helix bundle noted in the NMR structure determinations. Furthermore, the N-terminal helices of the two monomers occupy different positions relative to the three-helix core and are completely different from the NMR structures. The physiological significance of these structural differences is unknown.

scholarly journals Rational thermostabilisation of four-helix bundle dimeric de novo proteins

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Shin Irumagawa ◽  
Kaito Kobayashi ◽  
Yutaka Saito ◽  
Takeshi Miyata ◽  
Mitsuo Umetsu ◽  
...  
Keyword(s):  
Protein Design ◽  
De Novo ◽  
Protein Complexes ◽  
Salt Bridge ◽  
Dynamics Simulation ◽  
Saturation Mutagenesis ◽  
Helix Bundle ◽  
Stable Mutant ◽  
Four Helix Bundle ◽  
The Stability

AbstractThe stability of proteins is an important factor for industrial and medical applications. Improving protein stability is one of the main subjects in protein engineering. In a previous study, we improved the stability of a four-helix bundle dimeric de novo protein (WA20) by five mutations. The stabilised mutant (H26L/G28S/N34L/V71L/E78L, SUWA) showed an extremely high denaturation midpoint temperature (Tm). Although SUWA is a remarkably hyperstable protein, in protein design and engineering, it is an attractive challenge to rationally explore more stable mutants. In this study, we predicted stabilising mutations of WA20 by in silico saturation mutagenesis and molecular dynamics simulation, and experimentally confirmed three stabilising mutations of WA20 (N22A, N22E, and H86K). The stability of a double mutant (N22A/H86K, rationally optimised WA20, ROWA) was greatly improved compared with WA20 (ΔTm = 10.6 °C). The model structures suggested that N22A enhances the stability of the α-helices and N22E and H86K contribute to salt-bridge formation for protein stabilisation. These mutations were also added to SUWA and improved its Tm. Remarkably, the most stable mutant of SUWA (N22E/H86K, rationally optimised SUWA, ROSA) showed the highest Tm (129.0 °C). These new thermostable mutants will be useful as a component of protein nanobuilding blocks to construct supramolecular protein complexes.

scholarly journals A mixed chirality α-helix in a stapled bicyclic and a linear antimicrobial peptide revealed by X-ray crystallography

2021 ◽  
Author(s):  
Stéphane Baeriswyl ◽  
Hippolyte Personne ◽  
Ivan Di Bonaventura ◽  
Thilo Köhler ◽  
Christian van Delden ◽  
...  
Keyword(s):  
Antimicrobial Peptides ◽  
Antimicrobial Peptide ◽  
Crystal Structures ◽  
X Ray ◽  
X Ray Crystallography ◽  
Α Helix

We report the first X-ray crystal structures of mixed chirality α-helices comprising only natural residues as the example of bicyclic and linear membrane disruptive amphiphilic antimicrobial peptides containing seven l- and four d-residues.

De NovoDesign and Synthesis of Four α-Helix Bundle Proteins with Flavin Function

1993 ◽  
Vol 22 (9) ◽  
pp. 1533-1536 ◽  
Author(s):  
Hisakazu Mihara ◽  
Kin-ya Tomizaki ◽  
Norikazu Nishino ◽  
Tsutomu Fujimoto
Keyword(s):  
Helix Bundle ◽  
Α Helix

Self-Assembly of a Four-Helix Bundle on a DNA Quadruplex

2009 ◽  
Vol 48 (15) ◽  
pp. 2749-2751 ◽  
Author(s):  
Brooke A. Rosenzweig ◽  
Andrew D. Hamilton
Keyword(s):  
Self Assembly ◽  
Helix Bundle ◽  
Dna Quadruplex ◽  
Four Helix Bundle

Discriminatory Aspects of Pre-employment Screening: Low-Back X-ray Examinations in the Railroad Industry

1979 ◽  
Vol 5 (3) ◽  
pp. 197-214
Author(s):  
Paul H. Rockey ◽  
Jane Fantel ◽  
Gilbert S. Omenn
Keyword(s):  
Low Back Pain ◽  
Back Pain ◽  
Screening Program ◽  
Job Applicants ◽  
Radiation Hazard ◽  
Low Back ◽  
Negative Consequences ◽  
X Ray ◽  
Work Related ◽  
Increased Risk

AbstractIn screening the majority of job applicants, most of this nation's railroads administer a low-back X-ray examination in an attempt to ascertain the likelihood that the applicant will sustain future work-related low-back pain or injury. Many applicants are rejected for employment on the basis of the X-ray findings. The railroads apparently perceive this screening program as a cost-effective means (1) of decreasing the incidence of compensation claims for work-related injuries, brought against the rail-roads under the Federal Employers' Liability Act (FELA), (2) of reducing the number of lost workdays resulting from low-back pain or injury, and (3) of protecting particularly susceptible workers from job-related hazards.The authors of this Article submit that low-back X-ray examinations are poor predictors of future low-back pain or injury. They assert that the railroads' use of such examinations misclassifies a substantial number of job applicants as being at increased risk for such pain or injury, and, in consequence, unfairly denies them employment. Furthermore, the authors claim, the screening program has other negative consequences. For example, applicants rejected for railroad employment on the basis of X-ray findings may as a result have difficulty finding jobs in other industries. In addition, they state, there is a potential radiation hazard to examinees. Moreover, both the railroads and those applicants accepted for employment may inappropriately be reassured by normal findings.On balance, the authors conclude, the screening program has a negative social value. The authors suggest that the program, in effect, erroneously labels many applicants as handicapped, and then denies them employment. Such persons might have legal recourse under federal and state statutes prohibiting employment discrimination against the handicapped.

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