| Identifier | Protein names | Gene names | Cross reference refseq | Length | Species |
| P08523 | Olfactory marker protein; Olfactory neuronal-specific protein; | Omp; | NP_036748.1; | 163 | rat |
| Q65Z15 | Oncostatin-M; OSM; | Osm; | NP_001006962.1; | 239 | rat |
| P02631 | Oncomodulin; OM; Parvalbumin beta; | Ocm; | NP_037127.1; | 109 | rat |
| Q2TA68 | Dynamin-like 120 kDa protein, mitochondrial; EC 3.6.5.5; Optic atrophy protein 1 homolog; [Cleaved into: Dynamin-like 120 kDa protein, form S1]; | Opa1; | NP_598269.3;XP_006248560.1; | 960 | rat |
| P32736 | Opioid-binding protein/cell adhesion molecule; OBCAM; OPCML; Opioid-binding cell adhesion molecule; | Opcml; Obcam; | NP_446300.1; | 345 | rat |
| P0CAX5 | Oligophrenin-1; | Ophn1; | NP_001101318.1;XP_006257134.1; | 802 | rat |
| P97608 | 5-oxoprolinase; EC 3.5.2.9; 5-oxo-L-prolinase; 5-OPase; Pyroglutamase; | Oplah; | NP_446356.1;XP_006241836.1;XP_006241837.1; | 1288 | rat |
| Q8R456 | Melanopsin; Opsin-4; | Opn4; | NP_620215.1; | 474 | rat |
| P33533 | Delta-type opioid receptor; D-OR-1; DOR-1; Opioid receptor A; | Oprd1; Ror-a; | NP_036749.1; | 372 | rat |
| P34975 | Kappa-type opioid receptor; K-OR-1; KOR-1; | Oprk1; Ror-d; | NP_058863.1; | 380 | rat |
| P33535 | Mu-type opioid receptor; M-OR-1; MOR-1; Opioid receptor B; | Oprm1; Ror-b; | NP_001033686.1;NP_001033688.2;NP_001033689.1;NP_001033690.1;NP_037203.1; | 398 | rat |
| P35370 | Nociceptin receptor; Kappa-type 3 opioid receptor; KOR-3; Orphanin FQ receptor; ROR-C; XOR1; | Oprl1; Oor Oprl; | NP_113757.1;XP_006235798.1;XP_006235800.1; | 367 | rat |
| Q63652 | Short-wave-sensitive opsin 1; S opsin; Blue cone photoreceptor pigment; Blue-sensitive opsin; BOP; Short wavelength-sensitive cone opsin; | Opn1sw; Bcp; | NP_112277.1; | 346 | rat |
| P51489 | Rhodopsin; | Rho; | NP_254276.1; | 348 | rat |
| O35476 | Medium-wave-sensitive opsin 1; Green cone photoreceptor pigment; Green-sensitive opsin; Medium wavelength-sensitive cone opsin; | Opn1mw; Gcp; | NP_446000.1; | 359 | rat |
| Q8R5M4 | Optineurin; FIP-2-like protein; | Optn; | NP_659549.2; | 585 | rat |
| Q6AXR8 | Protein orai-3; Transmembrane protein 142C; | Orai3; Tmem142c; | NP_001014046.1; | 290 | rat |
| Q80Z32 | Origin recognition complex subunit 1; | Orc1; Orc1l; | NP_808792.1; | 848 | rat |
| Q75PQ8 | Origin recognition complex subunit 2; | Orc2; Orc2l; | NP_001012003.1;XP_006245018.1; | 576 | rat |
| Q4R180 | Origin recognition complex subunit 3; | Orc3; Orc3l; | NP_001020453.1; | 711 | rat |
