Biology subjects

Sadian, Y.

Publications and source records attributed to Sadian, Y..

3 recordsLinked to original sources

bioRxiv2022

Cryo-EM structure of the Rhodobaca bogoriensis RC-LH1-PufX dimeric complex at 2.9 angstrom

The reaction centre-light harvesting 1 (RC-LH1) complex is essential for converting light into proton motive force in photosynthetic bacteria. RC-LH1 is a monomer in most purple bacteria, but in Rhodobacter species, it is a dimer. Its assembly depends on an accessory polypeptide (PufX) and, ultimately, on photosynthetic growth. To date, knowledge on the RC-LH1-PufX structure, where the dimer has two incomplete C-shaped antenna rings surrounding an RC, is mainly limited to the model organism Rhodobacter sphaeroides. Here we present a cryo-electron microscopy structure at 2.9 [A] from Rhodobaca bogorensis strain LBB1. RCs are surrounded by 30 antennas and incorporate protein Y and PufX. RCs are stably connected by PufX, which self-interacts, electrostatically attracts cytochrome c2 (cyt c2) and forms extensive networks with co-factors. This structure underlines coordinated energy transfer in a combinatorial manner, providing a basis to describe bacterial photosynthesis within a dimeric photosynthetic apparatus.

biophysics↗

bioRxiv2021

The connecting cilium inner scaffold provides a structural foundation to maintain photoreceptor integrity

Retinal degeneration is a leading cause of human blindness due to progressive loss of ciliated photoreceptors cells. While this degradation can be associated with cohesion defects of the microtubule-based connecting cilium (CC) structure, the underlying mechanism is not understood. Here, using expansion microscopy and electron microscopy, we reveal the molecular architecture of the CC and demonstrate that microtubules are linked together by a CC-inner scaffold (CC-IS) containing POC5, CENTRIN and FAM161A. Monitoring CC-IS assembly during photoreceptor development in mouse reveals that it acts as a structural zipper, progressively bridging microtubule doublets and straightening the CC. Consistently, Fam161a mutations lead to a specific CC-IS loss and trigger microtubule doublets spreading, prior to outer segment collapse and photoreceptor degeneration, providing a molecular mechanism for retinitis pigmentosa disease. One Sentence SummaryThe connecting cilium inner scaffold acts as a structural zipper granting photoreceptor integrity.

cell biology↗

bioRxiv2018

Structural rearrangement of TFIIS- and TFIIF/TFIIE-like subunits in RNA polymerase I transcription complexes

RNA polymerase (Pol) I is a 14-subunit enzyme that solely transcribes pre-ribosomal RNA. Cryo-EM structures of Pol I initiation and elongation complexes have given first insights into the molecular mechanisms of Pol I transcription. Here, we present cryo-electron microscopy structures of yeast Pol I elongation complexes (ECs) bound to the nucleotide analog GMPCPP at 3.2 to 3.4 [A] resolution that provide additional insight into the functional interplay between the TFIIE/TFIIF-like A49-A34.5 heterodimer and the TFIIS-like subunit A12.2 present in Pol I. Strikingly, most of the nucleotide-bound ECs lack the A49-A34.5 heterodimer and adopt a Pol II-like conformation, in which the A12.2 C-terminal domain is bound in a previously unobserved position at the A135 surface. Our work suggests a regulatory mechanism of Pol I transcription where the association of the A49-A34.5 heterodimer to Pol I is regulated by subunit A12.2, thereby explaining in vitro biochemical and kinetic data.

molecular biology↗