Biology subjects

Roseman, A. M.

Publications and source records attributed to Roseman, A. M..

3 recordsLinked to original sources

bioRxiv2022

Fibrillin microfibril structure identifies long-range effects of inherited pathogenic mutations affecting a key regulatory TGFβ-binding site

Genetic mutations in fibrillin microfibrils cause a range of serious inherited diseases such as Marfan syndrome (MFS) and Weill-Marchesani syndrome (WMS). These diseases typically show major dysregulation of tissue development and growth, particularly in skeletal long bones, but links between the mutations and the diseases are unknown. In this study we reveal the detailed cryo-EM structure of native fibrillin microfibrils from mammalian tissue. The major bead region showed pseudo 8-fold symmetry and a buried protease resistant N-terminal core. Based on this structure, we show a WMS deletion mutant induces a rearrangement with long-range effects blocking interaction with latent TGF{beta}-binding protein (LTBP)-1 at a remote site. Separate deletion of this binding site resulted in the assembly of shorter fibrillin microfibrils with structural alterations. These results establish that in complex extracellular protein assemblies, such as in fibrillin, mutations may have long-range structural consequences to disrupt growth factor signalling and cause disease.

biochemistry↗

bioRxiv2021

Multi-modal adaptor-clathrin contacts drive coated vesicleassembly

Clathrin-coated pits are formed by the recognition of membrane and cargo by the heterotetrameric AP2 complex and the subsequent recruitment of clathrin triskelia. A potential role for AP2 in coated-pit assembly beyond initial clathrin recruitment has not been explored. Clathrin binds the {beta}2 subunit of AP2, and several binding sites on {beta}2 and on the clathrin heavy chain have been identified, but our structural knowledge of these interactions is incomplete and their functional importance during endocytosis is unclear. Here, we analysed the cryo-EM structure of clathrin cages assembled in the presence of {beta}2 hinge and appendage ({beta}2HA) domains. We find that the {beta}2-appendage binds in at least two positions in the cage, demonstrating that multi-modal binding is a fundamental property of clathrin-AP2 interactions. In one position, {beta}2-appendage cross-links two adjacent terminal domains from different triskelia below the vertex. Functional analysis of {beta}2HA-clathrin interactions reveals that endocytosis requires two clathrin interaction sites: a clathrin-box motif on the hinge and the "sandwich site" on the appendage, with the appendage "platform site" having less importance. From these studies and the work of others, we propose that {beta}2-appendage binding to more than one clathrin triskelion is a key feature of the system and likely explains why clathrin assembly is driven by AP2.

biochemistry↗

bioRxiv2018

The structural basis of translational control by eIF2 phosphorylation

Protein synthesis in eukaryotes is controlled by signals and stresses via a common pathway, called the integrated stress response (ISR). Phosphorylation of the translation initiation factor eIF2 alpha at a conserved serine residue mediates translational control at the ISR core. To provide insight into the mechanism of translational control we have determined the structures of eIF2 both in phosphorylated and unphosphorylated forms bound with its nucleotide exchange factor eIF2B by cryo-electron microscopy. The structures reveal that eIF2 undergoes large rearrangements to promote binding of eIF2 to the regulatory core of eIF2B comprised of the eIF2B alpha, beta and delta subunits. Only minor differences are observed between eIF2 and eIF2P binding to eIF2B suggesting that the higher affinity of eIF2P for eIF2B drives translational control. We present a model for controlled nucleotide exchange and initiator tRNA binding to the eIF2/eIF2B complex.

molecular biology↗