| Function/Process | Molecular role | Key partners/complexes | Experimental evidence (assay types) | Subcellular location | Notes | Primary citation (with year, DOI URL) |
|---|---|---|---|---|---|---|
| Golgi-to-prevacuolar/endosomal transport (CPY pathway) | Sec1/Munc18-family SM protein required for docking/fusion of Golgi-derived vesicles with the prevacuolar compartment; acts with endosomal SNARE machinery | Pep12p, Vti1p; functionally linked to Vps21/Ypt51 Rab5-like GTPase | Mutant phenotyping, epistasis, cargo-trafficking assays, comparison of intracellular vs endocytic routes (pqac-00000015, pqac-00000016, pqac-00000020) | Prevacuolar/endosomal compartment | Defines a VPS45-dependent intracellular route into the PVC distinct from plasma membrane-derived endocytic entry | Bryant et al. 1998, https://doi.org/10.1016/S0171-9335(98)80016-2 (pqac-00000015, pqac-00000016, pqac-00000020) |
| Endocytic entry to PVC | Not required for delivery of endocytosed cargo from plasma membrane to PVC | Endocytosed Ste3p cargo pathway is VPS45-independent | Endocytosis assays/cargo tracking showing Ste3p delivery without VPS45 (pqac-00000016) | Plasma membrane to PVC route | Separates biosynthetic Golgi→PVC fusion from endocytic traffic into the same compartment | Bryant et al. 1998, https://doi.org/10.1016/S0171-9335(98)80016-2 (pqac-00000016) |
| Cytoplasm-to-vacuole targeting (Cvt) of aminopeptidase I | Forms a functional t-SNARE–SM module that promotes a membrane-fusion step needed for constitutive API delivery | Tlg2p; separate Vps45p complexes with Tlg2p and Pep12p | Temperature-sensitive mutant analysis, pulse-chase API maturation, membrane fractionation, protease sensitivity/protection, native and denaturing immunoprecipitation, rapamycin bypass experiments (pqac-00000000, pqac-00000001, pqac-00000003, pqac-00000004, pqac-00000005) | Tlg2-associated Golgi/endosomal membranes and Cvt vesicles | Required for Cvt but dispensable for starvation-induced macroautophagy; vps45ts phenocopies tlg2Δ for API maturation defects | Abeliovich et al. 1999, https://doi.org/10.1093/emboj/18.21.6005 (pqac-00000000, pqac-00000001, pqac-00000003, pqac-00000004, pqac-00000005) |
| SNARE regulation with Tlg2p | Directly binds Tlg2p and positively regulates productive SNARE complex assembly | Tlg2p, Tlg1p, Vti1p | Co-precipitation/complex analysis, GST-binding, truncation mutants, subcellular fractionation (pqac-00000013, pqac-00000019) | Membrane-associated when full-length Tlg2p is present; becomes cytosolic with Tlg2 N-terminal truncation | Vps45p is needed not just for Tlg2 stability but also for Tlg2 entry into ternary SNARE complexes | Bryant & James 2001, https://doi.org/10.1093/emboj/20.13.3380 (pqac-00000013, pqac-00000019) |
| Tlg2p quality control/stability | Stabilizes the syntaxin homologue Tlg2p; prevents rapid proteasome-dependent loss of Tlg2p | Tlg2p; proteasome machinery | Immunoblotting in vps45Δ, proteasome-mutant rescue, pulse-chase degradation time course, fractionation (pqac-00000013, pqac-00000019, pqac-00000021) | Tlg2p still reaches correct intracellular location without Vps45p, but is unstable/nonfunctional | Loss of VPS45 causes rapid Tlg2 depletion detectable within ~20 min and near-complete loss by ~60 min after inactivation in reported assays | Bryant & James 2001, https://doi.org/10.1093/emboj/20.13.3380 (pqac-00000013, pqac-00000019, pqac-00000021) |
| Endosomal docking/fusion signal integration | Acts in Vac1p-, Rab-, and PI3P-coordinated docking/fusion at the endosome | Vac1p, Pep12p, Vps21p, Vps9p, VPS34/PI(3)P | Protein A pulldown/co-precipitation, mutant interaction analysis, nucleotide-state-specific Rab binding, FYVE-domain mutant analysis (pqac-00000014, pqac-00000017) | Endosome/prevacuolar endosome | Vac1p behaves as a multivalent adaptor linking PI3P and active Vps21 to Pep12/Vps45-dependent vesicle targeting | Peterson et al. 1999, https://doi.org/10.1016/S0960-9822(99)80071-2 (pqac-00000014, pqac-00000017) |
| Structural basis of SM–syntaxin recognition | SM protein recognizes the syntaxin N-terminal region; selective residues in Tlg2 homologs are important for Vps45 binding | Tlg2p/syntaxin 16–Vps45 interface | Structural/biochemical analysis of Tlg2p/syntaxin 16 binding determinants (pqac-00000012) | Endosomal SNARE interface | Provides mechanistic support for specificity of Vps45–Tlg2 interaction, complementing yeast functional genetics | Dulubova et al. 2002, https://doi.org/10.1093/emboj/cdf381 (pqac-00000012) |
| Current conceptual placement of Vps45 among SM proteins | Endosomal SM/Sec1-Munc18 chaperone that promotes SNARE assembly and membrane fusion; conceptually adjacent to short-range tethering functions of SM proteins | Endosomal SNAREs; compared with Sly1, Vps33, tethering complexes | Review synthesis and mechanistic extrapolation from contemporary SM/tether literature (pqac-00000006, pqac-00000007, pqac-00000008, pqac-00000009) | Endosomal compartments / endosomal recycling context | 2023–2024 sources emphasize SM proteins as active fusion chaperones rather than passive syntaxin binders; yeast Vps45 remains the endosomal SM benchmark | Szentgyörgyi & Spang 2023, https://doi.org/10.1242/jcs.260471; Duan et al. 2024, https://doi.org/10.1083/jcb.202001032 (pqac-00000006, pqac-00000007, pqac-00000008, pqac-00000009) |


*Table: This table summarizes experimentally supported functional annotation for S. cerevisiae VPS45/YGL095C, including pathway role, interacting partners, localization, and assay evidence. It is useful as a compact evidence map linking classical yeast genetics and biochemistry with current SM-protein conceptual frameworks.*