Biology subjects

Landau, M.

Publications and source records attributed to Landau, M..

4 recordsLinked to original sources

bioRxiv2018

Toxic Determinants of Staphylococcus aureus PSMα3 Cross-α Amyloid

The phenol-soluble modulin (PSM) peptide family, secreted by Staphylococcus aureus, performs various virulence activities, some mediated by the formation of amyloid fibrils of diverse architectures. Specifically, PSM1 and PSM4 structure the S. aureus biofilm by assembling into robust cross-{beta} amyloid fibrils. PSM3, the most cytotoxic member of the family, assembles into cross- fibrils in which -helices stack into tightly mated sheets, mimicking the cross-{beta} architecture. Here we demonstrated that massive T-cell deformation and death is linked with PSM3 aggregation and co-localization with cell membranes. Our extensive mutagenesis analyses supported the role of positive charges, and especially Lys17, in interactions with the membrane, and suggested their regulation by inter- and intra-helical electrostatic interactions within the cross- fibril. We hypothesize that PSM3 cytotoxicity is governed by the ability to form cross- fibrils and involves a dynamic process of co-aggregation with cell membrane, rupturing it. HighlightsO_LIThe cytotoxic S. aureus PSM3 assembles into cross- fibrils C_LIO_LICross- fibril polymorphism and mutations-induced secondary structure switching C_LIO_LIRegulation by cross- fibril inter- and intra-helical electrostatic interactions C_LIO_LIToxicity as a putative dynamic process of PSM3 co-aggregation with membranes C_LI

biochemistry↗

bioRxiv2018

Identification of two principal amyloid-driving segments in variable domains of Ig light chains in AL amyloidosis

Systemic light chain amyloidosis (AL) is a disease caused by overexpression of monoclonal immunoglobulin light chains that form pathogenic amyloid fibrils. These amyloid fibrils deposit in tissues and cause organ failure. Proteins form amyloid fibrils when they partly or fully unfold and expose segments capable of stacking into {beta}-sheets that pair forming a tight, dehydrated interface. These structures, termed steric zippers, constitute the spines of amyloid fibrils. Here, we identify segments within the variable domains of Ig light chains that drive the assembly of amyloid fibrils in AL. We demonstrate there are at least two such segments. Each one can drive amyloid fibril assembly independently of the other. Thus these two segments are therapeutic targets. In addition to elucidating the molecular pathogenesis of AL, these findings also provide an experimental approach to identify segments that drive fibril formation in other amyloid diseases.

biochemistry↗

bioRxiv2018

Extreme Amyloid Polymorphism in Staphylococcus aureus Virulent PSMα Peptides

Members of the Staphylococcus aureus phenol-soluble modulin (PSM) peptide family are secreted as functional amyloids that serve diverse roles in pathogenicity and may be present as full-length peptides or as naturally occurring truncations. We recently showed that the activity of PSM3, the most toxic member, stems from the formation of cross- fibrils, which are at variance with the cross-{beta} fibrils linked with eukaryotic amyloid pathologies. Here, we show that PSM1 and PSM4, involved in biofilm structuring, form canonical cross-{beta} amyloid fibrils wherein {beta}-sheets tightly mate through steric zipper interfaces, conferring high stability. Contrastingly, a truncated PSM3 has antibacterial activity, forms reversible fibrils, and reveals two polymorphic and atypical {beta}-rich fibril architectures. These architectures are radically different from both the cross- fibrils formed by full-length PSM3, and from the canonical cross-{beta} fibrils. Our results point to structural plasticity being at the basis of the functional diversity exhibited by S. aureus PSMs.

biochemistry↗

bioRxiv2017

Insights into DNA substrate selection by APOBEC3G from structural, biochemical, and functional studies.

Human apolipoprotein B mRNA-editing enzyme-catalytic polypeptide-like 3 (A3) proteins are a family of cytidine deaminases that catalyze the conversion of cytidine to uridine in single-stranded DNA (ssDNA). A3 proteins act in the innate immune response to viral infection by mutating the viral ssDNA. One of the most well-studied human A3 family members is A3G, which is a potent inhibitor of HIV-1. Each A3 protein prefers a specific substrate sequence for catalysis - for example, A3G deaminates the third cytidine in the CCCA sequence motif. However, the interaction between A3G and ssDNA is difficult to characterize due to poor solution behavior of the full-length protein and loss of DNA affinity of the truncated protein. Here, we present a novel DNA-anchoring fusion strategy, which we have used to capture an A3G-ssDNA interaction. We characterized an A3G-DNA binding pocket that is important for the enzyme to scan the DNA for its hotspot. The results provide insights into the mechanism by which A3G selects and deaminates its preferred substrates and help define how A3 proteins are tailored to recognize specific DNA sequences. This knowledge contributes to a better understanding of the mechanism of DNA substrate selection by A3G, as well as A3G antiviral activity against HIV-1.

biophysics↗