| Property | Description | Evidence/Citations |
|---|---|---|
| Gene name/synonyms | Human **TRAPPC13** encodes **trafficking protein particle complex subunit 13**; the target identity is consistent with the human TRAPPIII-specific subunit discussed in structural and review literature. The user-provided synonym is **C5orf44**. | (pqac-00000000, pqac-00000013) |
| Protein complex membership | TRAPPC13 is a **metazoan TRAPPIII-specific subunit**. TRAPPIII in humans/metazoans comprises the shared TRAPP core plus **TRAPPC8, TRAPPC11, TRAPPC12, and TRAPPC13**. | (pqac-00000004, pqac-00000006, pqac-00000012, pqac-00000013) |
| Structural role in complex | Cryo-EM places TRAPPC13, together with **TRAPPC12**, at the **vertex/joint** where the **TRAPPC8** and **TRAPPC11** arms meet, helping organize the triangular TRAPPIII architecture. TRAPPC13 is therefore best understood as a **structural/accessory subunit** rather than the catalytic GEF center. | (pqac-00000007, pqac-00000013, pqac-00000017) |
| Subcellular localization | TRAPPC13 acts as part of TRAPPIII on **membrane trafficking compartments of the early secretory pathway**, especially the **ER-Golgi interface / ERGIC / Golgi-associated membranes**, and in **autophagy-related membranes** where Rab1 is activated. The exact localization evidence is mainly at the **complex** level rather than TRAPPC13 alone. | (pqac-00000003, pqac-00000006, pqac-00000012, pqac-00000018) |
| Primary molecular function | TRAPPC13 does **not itself catalyze nucleotide exchange**; instead it contributes to the **assembly/stability/organization of the TRAPPIII Rab1 GEF complex**. Through TRAPPIII, it supports activation of **Rab1** by promoting the complex architecture needed for membrane trafficking and autophagy in vivo. | (pqac-00000003, pqac-00000013, pqac-00000018, pqac-00000020) |
| Biological processes | By virtue of its role in TRAPPIII, TRAPPC13 is implicated in **ER-to-Golgi transport**, **early secretory pathway organization**, **Golgi homeostasis**, and **autophagosome formation/autophagy**. | (pqac-00000000, pqac-00000003, pqac-00000006, pqac-00000012, pqac-00000020) |
| Substrate specificity | TRAPPC13 has **no independent substrate specificity** known. At the complex level, **TRAPPIII is the physiological GEF for Rab1** in metazoans; Rab1 is the relevant small GTPase substrate for the TRAPPC13-containing complex. | (pqac-00000003, pqac-00000004, pqac-00000013, pqac-00000020) |
| Essential for viability | Recent reviews summarize TRAPPC13 as **non-essential for viability in human cell lines**, in contrast to TRAPPC8 and TRAPPC11, which are reported as essential for Rab1 recruitment/activity in vivo. Consistent with this, TRAPPIII lacking TRAPPC12/TRAPPC13 retained Rab1 GEF activity in vitro in a recombinant “miniTRAPPIII” preparation. | (pqac-00000008, pqac-00000013) |
| Disease associations | As of recent reviews, there are **no specific monogenic human disease associations reported for TRAPPC13**, unlike several other TRAPP subunits. Reviews of TRAPPopathies explicitly note **no reported disease associations** for TRAPPC13. | (pqac-00000005, pqac-00000000) |
| Tissue expression pattern | TRAPPC13 is reported to be **relatively ubiquitously expressed** across human tissues, with some tissues showing higher expression than others; however, recent reviews emphasize that detailed functional and disease data remain limited. | (pqac-00000000) |


*Table: This table summarizes the best-supported structural and functional features of human TRAPPC13 based on recent TRAPP-complex literature. It highlights what is established directly from cryo-EM and biochemical studies, while distinguishing areas where evidence is still limited or inferential.*