Structural determinants of co-translational protein complex assembly

The assembly of proteins into functional complexes is critical to lifes processes. While textbooks depict complex assembly as occurring between fully synthesized proteins, we know today that thousands of proteins in the human proteome assemble co-translationally during their synthesis. Why this process takes place, however, remains unknown. We show that co-translational assembly is governed by biophysical and structural characteristics of the protein complex, and involves mutually stabilized, intertwined subunits. Consequently, these subunits are also co-regulated across the central dogma, from transcription to protein degradation. Leveraging structural signatures with AlphaFold2-based predictions enables us to accurately predict co-translational assembly on a proteome-wide scale, which we validated by ribosome profiling, genetic perturbations, and smFISH experiments. Notably, the latter showed that co-translationally assembling subunits exhibit co-localized mRNAs. This work unveils a fundamental connection between protein structure and the translation process, highlighting the overarching impact of three-dimensional structure on gene expression, mRNA localization, and proteostasis. One Sentence SummaryProtein complexes with topologically intertwined subunits require co-translational assembly and synchronized proteostasis of subunits, with implications in protein stability, mRNA localization, and evolution. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=195 SRC="FIGDIR/small/576408v1_ufig1.gif" ALT="Figure 1"> View larger version (62K): org.highwire.dtl.DTLVardef@712a2org.highwire.dtl.DTLVardef@58894borg.highwire.dtl.DTLVardef@9db5c6org.highwire.dtl.DTLVardef@8eae4_HPS_FORMAT_FIGEXP M_FIG C_FIG