Panel A: A flowchart illustrating six core insertion reactions. The reactions are labeled 1 through 6 and involve different components like Sec61 and Oxa1 family insertases. Each reaction is depicted with arrows indicating the direction of the process and includes labels for single-pass (SP) and multipass (MP) proteins. The number of instances in the human proteome and average Gapp values for each reaction are provided. Panel B: A proportional area chart showing the reactions are grouped by two major translocation machineries: EMC/GET/GEL (Oxa1 family) and Sec61.
Six core reactions for membrane protein insertion. (A) Models of the six core insertion reactions that occur during membrane protein biogenesis. Reactions 1–4 apply to both SP and MP proteins; reactions 5–6 only apply to MP proteins. Reactions 1, 2, and 5 require Sec61, whereas reactions 3, 4, and 6 involve Oxa1 family insertases. Charge biases are indicated on the substrate. The number of instances in the human proteome of each reaction and average ΔGapp for those set of TMDs are indicated. (B) Proportional area chart showing the relative contribution of each reaction to the total membrane proteome, subdivided by SP (blue) and MP (red) proteins. Reactions are grouped by the two major translocation machineries: EMC/GET/GEL (Oxa1 family, left) versus Sec61 (right). This chart visually illustrates that the majority of Oxa1 family reactions operate on MP proteins, whereas the majority of Sec61-mediated reactions operate on SP membrane proteins. TMD-pair insertion is by far the most common insertion reaction during biogenesis of the membrane proteome. SP, single pass; MP, multipass.