A nuclear-encoded factor implicated in coordination of photosystem II assembly and psbA messenger RNA biological translation.^[ref]

Clathrin assembles a scaffold around selected membrane buds. Cargo recognition generally depends on associated adaptors, so the scaffold alone neither selects every cargo nor specifies every destination.

Antizyme is a regulatory protein that binds ornithine decarboxylase, inhibits its activity and promotes its degradation. This limits a key entry step in polyamine synthesis. Production of antizyme itself can respond to polyamine availability through regulated biological translation, creating feedback between a metabolic product and the lifetime of its biosynthetic enzyme. The inhibitory protein is therefore part of a pathway-control system rather than an additional substrate of the decarboxylase reaction. ^[ref]

A regulatory protein whose association with a cyclin-dependent kinase influences kinase activity and substrate control during the cell cycle.

A regulated protease that promotes sister-chromatid separation by cleaving the remaining cohesion-bearing kleisin subunit of cohesin.

A ligand for PD-1 expressed in some tumours and normal tissues; its interaction can restrain T-cell activity.

An inhibitory regulator of separase. Its regulated destruction helps permit sister-chromatid separation.

Destruction is controlled by the anaphase-promoting complex, linking the cell-cycle decision to activation of the protease that removes a cohesion barrier. This makes protein turnover part of a switch that permits physical chromosome separation. ^[ref]

A cytokinetic protein complex coupling spindle organisation to cortical signalling, including regulation of ECT2-dependent RhoA activation.

A guanine-nucleotide exchange factor involved in local activation of RhoA during animal cytokinesis.

Spatially restricted RhoA activation helps organize the contractile machinery at the cleavage site. The exchange factor therefore links positional information from the division apparatus to local cytoskeletal force generation. ^[ref]

A small GTPase that promotes actin assembly and myosin regulation during contractile-ring formation and other cellular processes.

A membrane-remodelling protein system involved in processes including the final membrane constriction and separation of animal cytokinesis.

A protein that binds and protects single-stranded DNA while influencing its accessibility to replication and repair machinery.

A eukaryotic single-stranded DNA-binding complex participating in replication, repair and signalling responses.

Binding protects exposed single-stranded DNA and helps recruit other factors. Its presence can reflect normal replication or a response to damaged or stalled DNA structures, so it is not a unique marker of one pathway. ^[ref]

A cell–cell adhesion protein important in epithelial organisation. Its loss can affect tissue behaviour but alone does not identify every transition-associated state.

An intermediate-filament protein often used as one mesenchymal-associated marker. Its expression alone is not a complete definition of epithelial–mesenchymal transition.

A component required for conventional stable MHC class I surface complexes; its loss can impair recognition by peptide–MHC-I-dependent T cells.

Hfq is a bacterial RNA-binding protein that can facilitate interactions between regulatory RNAs and target transcripts. Its contribution depends on the particular RNA pair and does not make every Hfq-dependent expression change a direct binding effect.

Limited proteolysis cleaves a protein under controlled conditions to probe exposed regions or recover stable domains. Resistance can reflect accessibility and dynamics as well as sequence specificity of the chosen protease.

Directed evolution iterates sequence diversification, functional screening or selection, and recovery of successful variants. A reliable genotype–phenotype link and an assay faithful to the desired property are more important than library size alone.

Rational protein design proposes sequences or substitutions using structural, chemical or evolutionary information. A plausible model narrows the search but does not establish that the resulting protein folds, binds or catalyses as intended.