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Full-Text Articles in Physics

Morphological Transformations In The Magnetite Biomineralizing Protein Mms6 In Iron Solutions: A Small-Angle X-Ray Scattering Study, Honghu Zhang, Xunpei Liu, Shuren Feng, Wenjie Wang, Klaus Schmidt-Rohr, Mufit Akinc, Marit Nilsen-Hamilton, David Vaknin, Surya K. Mallapragada Jan 2015

Morphological Transformations In The Magnetite Biomineralizing Protein Mms6 In Iron Solutions: A Small-Angle X-Ray Scattering Study, Honghu Zhang, Xunpei Liu, Shuren Feng, Wenjie Wang, Klaus Schmidt-Rohr, Mufit Akinc, Marit Nilsen-Hamilton, David Vaknin, Surya K. Mallapragada

Biochemistry, Biophysics and Molecular Biology Publications

Magnetotactic bacteria that produce magnetic nanocrystals of uniform size and well-defined morphologies have inspired the use of biomineralization protein Mms6 to promote formation of uniform magnetic nanocrystals in vitro. Small angle X-ray scattering (SAXS) studies in physiological solutions reveal that Mms6 forms compact globular three-dimensional (3D) micelles (approximately 10 nm in diameter) that are, to a large extent, independent of concentration. In the presence of iron ions in the solutions, the general micellar morphology is preserved, however, with associations among micelles that are induced by iron ions. Compared with Mms6, the m2Mms6 mutant (with the sequence of hydroxyl/carboxyl containing ...


Interfacial Properties And Iron Binding To Bacterial Proteins That Promote The Growth Of Magnetite Nanocrystals: X-Ray Reflectivity And Surface Spectroscopy Studies, Wenjie Wang, Wei Bu, Lijun Wang, Pierre E. Palo, Surya K. Mallapragada, Marit Nilsen-Hamilton, David Vaknin Jan 2012

Interfacial Properties And Iron Binding To Bacterial Proteins That Promote The Growth Of Magnetite Nanocrystals: X-Ray Reflectivity And Surface Spectroscopy Studies, Wenjie Wang, Wei Bu, Lijun Wang, Pierre E. Palo, Surya K. Mallapragada, Marit Nilsen-Hamilton, David Vaknin

Biochemistry, Biophysics and Molecular Biology Publications

Surface sensitive X-ray scattering and spectroscopic studies have been conducted to determine structural properties of Mms6, the protein in Magnetospirillum magneticum AMB-1 that is implicated as promoter of magnetite nanocrystals growth. Surface pressure versus molecular area isotherms indicate Mms6 forms stable monolayers at the aqueous/vapor interface that are strongly affected by ionic conditions of the subphase. Analysis of X-ray reflectivity from the monolayers shows that the protein conformation at the interface depends on surface pressure and on the presence of ions in the solutions, in particular of iron ions and its complexes. X-ray fluorescence at grazing angles of incidence ...


Self-Assembly And Biphasic Iron-Binding Characteristics Of Mms6, A Bacterial Protein That Promotes The Formation Of Superparamagnetic Magnetite Nanoparticles Of Uniform Size And Shape, Lijun Wang, Tanya Prozorov, Pierre E. Palo, Xunpei Liu, David Vaknin, Ruslan Prozorov, Surya K. Mallapragada, Marit Nilsen-Hamilton Jan 2012

Self-Assembly And Biphasic Iron-Binding Characteristics Of Mms6, A Bacterial Protein That Promotes The Formation Of Superparamagnetic Magnetite Nanoparticles Of Uniform Size And Shape, Lijun Wang, Tanya Prozorov, Pierre E. Palo, Xunpei Liu, David Vaknin, Ruslan Prozorov, Surya K. Mallapragada, Marit Nilsen-Hamilton

Biochemistry, Biophysics and Molecular Biology Publications

Highly ordered mineralized structures created by living organisms are often hierarchical in structure with fundamental structural elements at nanometer scales. Proteins have been found responsible for forming many of these structures, but the mechanisms by which these biomineralization proteins function are generally poorly understood. To better understand its role in biomineralization, the magnetotactic bacterial protein, Mms6, which promotes the formation in vitro of superparamagnetic magnetite nanoparticles of uniform size and shape, was studied for its structure and function. Mms6 is shown to have two phases of iron binding: one high affinity and stoichiometric and the other low affinity, high capacity ...


Crystal Structure Of The Cusba Heavy-Metal Efflux Complex Of Escherichia Coli, Chih-Chia Su, Feng Long, Michael T. Zimmermann, Kanagalaghatta R. Rajashankar, Robert L. Jernigan, Edward W. Yu Jan 2011

Crystal Structure Of The Cusba Heavy-Metal Efflux Complex Of Escherichia Coli, Chih-Chia Su, Feng Long, Michael T. Zimmermann, Kanagalaghatta R. Rajashankar, Robert L. Jernigan, Edward W. Yu

Biochemistry, Biophysics and Molecular Biology Publications

Gram-negative bacteria, such as Escherichia coli, expel toxic chemicals via tripartite efflux pumps spanning both the inner and outer membranes. The three parts are: 1) a membrane fusion protein connecting 2) a substrate-binding inner membrane transporter to 3) an outer membrane-anchored channel in the periplasmic space. A crystallographic model of this tripartite efflux complex has been unavailable simply because co-crystallization of different components of the system has proven to be extremely difficult. We previously described the crystal structures of both the inner membrane transporter CusA1 and membrane fusion protein CusB2 of the CusCBA efflux system3,4 from ...


Crystal Structures Of The Cusa Efflux Pump Suggest Methionine-Mediated Metal Transport, Feng Long, Chih-Chia Su, Michael T. Zimmermann, Scott E. Boyken, Kanagalaghatta R. Rajashankar, Robert L. Jernigan, Edward W. Yu Jan 2010

Crystal Structures Of The Cusa Efflux Pump Suggest Methionine-Mediated Metal Transport, Feng Long, Chih-Chia Su, Michael T. Zimmermann, Scott E. Boyken, Kanagalaghatta R. Rajashankar, Robert L. Jernigan, Edward W. Yu

Biochemistry, Biophysics and Molecular Biology Publications

Gram-negative bacteria, such as Escherichia coli, frequently utilize tripartite efflux complexes in the resistance-nodulation-cell division (RND) family to expel diverse toxic compounds from the cell.1,2 The efflux system CusCBA is responsible for extruding biocidal Cu(I) and Ag(I) ions.3,4 No prior structural information was available for the heavy-metal efflux (HME) subfamily of the RND efflux pumps. Here we describe the crystal structures of the inner membrane transporter CusA in the absence and presence of bound Cu(I) or Ag(I). These CusA structures provide important new structural information about the HME sub-family of RND efflux ...