Category: Science

Wait, What? One Amino Acid in a Human Protein Is Built After the Ribosome Has Finished Most amino acids in a protein are selected during translation from the genetic code. Hypusine is different. The ribosome first places a lysine into eIF5A, and enzymes later remodel that lysine using part of spermidine. The result is one…

Wait, What? NEDD8 Can Make a Ubiquitin Ligase Better at Ubiquitinating Something Else It sounds circular: attach a ubiquitin-like protein to a ubiquitin-ligase scaffold so that the ligase can attach ubiquitin to another protein. That is exactly why NEDDylation is worth learning carefully. The central targets are cullins, structural backbones of cullin–RING ligases. NEDD8 attachment…

Wait, What? A Ribosome Can Be Marked Because It Is Stuck Beside a Membrane A ribosome is usually taught as a machine that reads mRNA and makes protein. At the endoplasmic reticulum, however, a ribosome can also become part of a membrane-quality-control problem. If translation stalls while a nascent chain is being threaded through the…

Distinct learning-progression job: Build reasoning from the question “how does a bacterium form the correct disulfide bonds in proteins that are being exported into an oxidizing periplasm?” to DsbA thiol–disulfide exchange, DsbB reoxidation by quinones, respiratory-chain coupling, incorrect-bond repair by DsbC, DsbD-mediated delivery of cytoplasmic reducing power, DsbG-related quality control, alternative VKOR pathways and the…

Distinct learning-progression job: Build reasoning from the question “what exactly happens when a ribosome reaches UAA, UAG or UGA?” to eRF1/eRF3 stop-codon decoding, GTP-triggered rearrangement, GGQ-mediated peptide release, ABCE1 binding and Fe–S-domain function, ATP-driven 80S splitting, eIF2D/MCT1–DENR-mediated post-recycling cleanup, transition toward new initiation and the fidelity boundary among normal termination, readthrough, NMD and ribosome rescue.…

Distinct learning-progression job: Build reasoning from the question “how does a mitochondrion assemble the rotary enzyme that makes most cellular ATP without allowing partial rotor or catalytic modules to short-circuit proton motive force?” to F1 catalytic-module construction, ATPAF1/ATPAF2/FMC1 chaperoning, c8-ring formation with TMEM70/TMEM242, mtDNA-encoded ATP6/ATP8 incorporation, peripheral-stalk assembly, monomer completion, dimer formation and the architectural…