| O-acetyl-ADP-ribose deacetylase 1 | OARD1 | C9IZY1 | 1 |
| Obg-like ATPase 1 (Fragment) | OLA1 | C9JTK6 | 1 |
| Obscurin | OBSCN | H3BPX2 | 1 |
| Occludin | OCLN | B5BU70 | 1 |
| Occludin | OCLN | A0A0G2JMZ8 | 1 |
| Occludin/ELL domain-containing protein 1 | OCEL1 | Q9H607 | 1 |
| OCIA domain-containing protein 1 (Fragment) | OCIAD1 | D6RG39 | 1 |
| Olfactory receptor 10A7 (Olfactory receptor OR12-6) | OR10A7 | Q8NGE5 | 1 |
| Olfactory receptor 11H4 (Olfactory receptor OR14-36) | OR11H4 | Q8NGC9 | 1 |
| Olfactory receptor 11L1 | OR11L1 | Q8NGX0 | 1 |
| Olfactory receptor 13C3 (Olfactory receptor OR9-8) | OR13C3 | Q8NGS6 | 1 |
| Olfactory receptor 14C36 (Olfactory receptor 5BF1) (Olfactory receptor OR1-59) | OR14C36 OR5BF1 | Q8NHC7 | 1 |
| Olfactory receptor 1D2 (Olfactory receptor 17-4) (OR17-4) (Olfactory receptor OR17-6) (Olfactory receptor-like protein HGMP07E) | OR1D2 OLFR1 | P34982 | 1 |
| Olfactory receptor 1E1 (Olfactory receptor 13-66) (OR13-66) (Olfactory receptor 17-2/17-32) (OR17-2) (OR17-32) (Olfactory receptor 1E5) (Olfactory receptor 1E6) (Olfactory receptor 5-85) (OR5-85) (Olfactory receptor OR17-18) (Olfactory receptor-like protein HGMP07I) | OR1E1 OR1E5 OR1E6 OR1E9P | P30953 | 1 |
| Olfactory receptor 1K1 | OR1K1 | Q8NGR3 | 1 |
| Olfactory receptor 1M1 (Olfactory receptor 19-6) (OR19-6) (Olfactory receptor OR19-5) | OR1M1 | Q8NGA1 | 1 |
| Olfactory receptor 2B6 (Hs6M1-32) (Olfactory receptor 2B1) (Olfactory receptor 2B5) (Olfactory receptor 5-40) (OR5-40) (Olfactory receptor 6-31) (OR6-31) (Olfactory receptor OR6-4) | OR2B6 OR2B1 OR2B1P OR2B5 OR2B6P | P58173 | 1 |
| Olfactory receptor 2M5 | OR2M5 OR2M5P | A3KFT3 | 1 |
| Olfactory receptor 2S2 (Olfactory receptor OR9-3) | OR2S2 | Q9NQN1 | 1 |
| Olfactory receptor 2T11 (Olfactory receptor OR1-65) | OR2T11 | Q8NH01 | 1 |
| Olfactory receptor 2T6 (OST703) (Olfactory receptor 2T9) | OR2T6 OR2T6P OR2T9 | Q8NHC8 | 1 |
| Olfactory receptor 2V2 (Olfactory receptor 2V3) (Olfactory receptor OR5-3) | OR2V2 OR2V3 | Q96R30 | 1 |
| Olfactory receptor 2W3 (Olfactory receptor 2W8) (Olfactory receptor OR1-49) | OR2W3 OR2W3P OR2W8P | Q7Z3T1 | 1 |
| Olfactory receptor 4F21 | OR4F21 OR4F21P | O95013 | 1 |
| Olfactory receptor 4K14 (Olfactory receptor OR14-22) | OR4K14 | Q8NGD5 | 1 |
| Olfactory receptor 51F1 | OR51F1 OR51F1P | A6NGY5 | 1 |
| Olfactory receptor 51L1 (Olfactory receptor OR11-31) | OR51L1 | Q8NGJ5 | 1 |
| Olfactory receptor 52E4 (Olfactory receptor OR11-55) | OR52E4 | Q8NGH9 | 1 |
| Olfactory receptor 5AC2 (HSA1) | OR5AC2 | Q9NZP5 | 1 |
| Olfactory receptor 5B12 (Olfactory receptor 5B16) (Olfactory receptor OR11-241) | OR5B12 OR5B12P OR5B16 | Q96R08 | 1 |
| Olfactory receptor 5B2 (OST073) (Olfactory receptor OR11-240) | OR5B2 | Q96R09 | 1 |
| Olfactory receptor 5H2 (Olfactory receptor OR3-10) | OR5H2 | Q8NGV7 | 1 |
| Olfactory receptor 5L1 (OST262) (Olfactory receptor OR11-151) | OR5L1 | Q8NGL2 | 1 |
| Olfactory receptor 5P3 (Olfactory receptor OR11-94) (Olfactory receptor-like protein JCG1) | OR5P3 | Q8WZ94 | 1 |
| Olfactory receptor 6C3 (HSA8) | OR6C3 | Q9NZP0 | 1 |
| Olfactory receptor 6J1 (Olfactory receptor 6J2) | OR6J1 OR6J2 | Q8NGC5 | 1 |
| Olfactory receptor 8K5 (Olfactory receptor OR11-174) | OR8K5 | Q8NH50 | 1 |
| Olfactory receptor 9A4 (Olfactory receptor OR7-1) | OR9A4 | Q8NGU2 | 1 |
| Olfactory receptor 9G4 (Olfactory receptor OR11-216) | OR9G4 | Q8NGQ1 | 1 |
| Oligodendrocyte transcription factor 2 (Oligo2) (Class B basic helix-loop-helix protein 1) (bHLHb1) (Class E basic helix-loop-helix protein 19) (bHLHe19) (Protein kinase C-binding protein 2) (Protein kinase C-binding protein RACK17) | OLIG2 BHLHB1 BHLHE19 PRKCBP2 RACK17 | Q49AL3 | 1 |
| Oligoribonuclease, mitochondrial (REXO2 protein) | REXO2 | Q9BTR4 | 1 |
| Omega-amidase NIT2 (Fragment) | NIT2 | H7C579 | 1 |
| Oncomodulin-1 (OM) (Parvalbumin beta) | OCM OCM1 OCMN | P0CE72 | 1 |
| Oncostatin-M (OSM) | OSM | P13725 | 1 |
| Opiorphin prepropeptide (Basic proline-rich lacrimal protein) (Proline-rich protein 1) (PRL1) [Cleaved into: Opiorphin] | OPRPN BPLP PROL1 | Q99935 | 1 |
| Opticin (Oculoglycan) | OPTC OPT | Q9UBM4 | 1 |
| Optineurin (Fragment) | OPTN | A0A087WY28 | 1 |
| Oral cancer-overexpressed protein 1 (cDNA FLJ58145, highly similar to Oral cancer overexpressed protein 1) | ORAOV1 | B4DFA5 | 1 |
| Oral-facial-digital syndrome 1 protein | OFD1 | A0A0A0MS89 | 1 |
| Organic solute transporter subunit beta (OST-beta) (Solute carrier family 51 subunit beta) | SLC51B OSTB | Q86UW2 | 1 |
| Origin recognition complex subunit 1 (Replication control protein 1) | ORC1 ORC1L PARC1 | Q13415 | 1 |
| Origin recognition complex subunit 6 | ORC6 ORC6L | Q9Y5N6 | 1 |
| Ornithine decarboxylase antizyme 2 (AZ2) (ODC-Az 2) | OAZ2 | O95190 | 1 |
| Ornithine decarboxylase antizyme 3 (AZ3) (ODC-Az 3) | OAZ3 | Q9UMX2 | 1 |
| Orofacial cleft 1 candidate gene 1 protein (Fragment) | OFCC1 | H7C4X1 | 1 |
| Orofacial cleft 1 candidate gene 1 protein (Orofacial clefting chromosomal breakpoint region candidate 1 protein) | OFCC1 MRDS1 | Q8IZS5 | 1 |
| Osteoclast stimulatory transmembrane protein (OC-STAMP) | OCSTAMP C20orf123 | Q9BR26 | 1 |
| Osteocrin (Musclin) [Cleaved into: Processed Osteocrin] | OSTN | P61366 | 1 |
| Osteopontin (Fragment) | SPP1 | D6R9C5 | 1 |
| Otolin-1 | OTOL1 | A6NHN0 | 1 |
| Otopetrin-3 | OTOP3 | Q7RTS5 | 1 |
| Otoraplin (Fibrocyte-derived protein) (Melanoma inhibitory activity-like protein) | OTOR FDP MIAL UNQ3054/PRO9873 | Q9NRC9 | 1 |
| OTU domain containing 7B (OTU domain-containing protein 7B) (Fragment) | OTUD7B RP11-212K13.2-003 | Q5SZ59 | 1 |
| OTU domain-containing protein 6A (EC 3.4.19.12) (DUBA-2) | OTUD6A DUBA2 | Q7L8S5 | 1 |
| Out at first protein homolog | OAF | E9PJ29 | 1 |
| Outer dense fiber protein 1 (Heat shock protein beta-10) (HspB10) | ODF1 HSPB10 ODFP | Q14990 | 1 |
| Outer dense fiber protein 2 (Cenexin) (Outer dense fiber of sperm tails protein 2) | ODF2 | B4DX73 | 1 |
| Outer dense fiber protein 3B (Fragment) | ODF3B | C9JUR5 | 1 |
| Ovochymase-1 (EC 3.4.21.-) | OVCH1 | Q7RTY7 | 1 |
| Ovochymase-2 | OVCH2 | A0A087X1V8 | 1 |
| Ovochymase-2 (EC 3.4.21.-) (Oviductin) | OVCH2 OVTN | Q7RTZ1 | 1 |
| Ovostatin homolog 1 | OVOS1 | Q6IE37 | 1 |
| OX-2 membrane glycoprotein (Fragment) | CD200 | U3KQQ2 | 1 |
| Oxidation resistance protein 1 | OXR1 | E9PLW2 | 1 |
| Oxidative stress-induced growth inhibitor 2 (hT41) | OSGIN2 C8orf1 | Q9Y236 | 1 |
| Oxysterol-binding protein | OSBPL1A hCG_2020467 | Q6GSK5 | 1 |
| Oxysterol-binding protein-related protein 1 | OSBPL1A | J3QS61 | 1 |
| Oxysterol-binding protein-related protein 9 | OSBPL9 | E9PK98 | 1 |
| P antigen family member 2 (PAGE-2) (G antigen family C 2) (Prostate-associated gene 2 protein) | PAGE2 GAGEC2 GAGEE2 | Q7Z2X7 | 1 |
| p-glycoprotein (Fragment) | MDR1 | Q6RVA0 | 1 |
| P-selectin (Fragment) | SELP | Q5R349 | 1 |
| p24B protein (Fragment) | 0 | Q9UMB6 | 1 |
| P2X purinoceptor 4 | P2RX4 | F6SFZ6 | 1 |
| P2X purinoceptor 4 (P2X4) (ATP receptor) (Purinergic receptor) | P2RX4 | Q5U089 | 1 |
| P2Y purinoceptor 12 (P2Y12) (ADP-glucose receptor) (ADPG-R) (P2T(AC)) (P2Y(AC)) (P2Y(cyc)) (P2Y12 platelet ADP receptor) (P2Y(ADP)) (SP1999) | P2RY12 HORK3 | Q9H244 | 1 |
| p53-activated protein-2 | PAP2 | Q8NEW2 | 1 |
| p53-induced death domain-containing protein 1 (Leucine-rich repeat and death domain-containing protein) | PIDD1 LRDD PIDD | Q9HB75 | 1 |
| p67 | 0 | Q13041 | 1 |
| PAI-1 mRNA-binding protein variant (cDNA, FLJ92551, Homo sapiens PAI-1 mRNA-binding protein (PAI-RBP1), mRNA) | 0 | Q5VU21 | 1 |
| Paired box protein Pax-5 (Fragment) | PAX5 | H0YB47 | 1 |
| Paired box protein Pax-6 (Aniridia type II protein) (Oculorhombin) | PAX6 AN2 | P26367 | 1 |
| Paired box protein Pax-7 (HuP1) | PAX7 HUP1 | P23759 | 1 |
| Paired box protein Pax-8 | PAX8 | Q06710 | 1 |
| Paired mesoderm homeobox protein 2A (ARIX1 homeodomain protein) (Aristaless homeobox protein homolog) (Paired-like homeobox 2A) | PHOX2A ARIX PMX2A | O14813 | 1 |
| PALM2-AKAP2 readthrough (Fragment) | PALM2-AKAP2 | B1ALY0 | 1 |
| Palmdelphin (Paralemmin-like protein) | PALMD C1orf11 PALML | Q9NP74 | 1 |
| Palmitoyl-protein thioesterase 1 (Fragment) | PPT1 | E9PIA8 | 1 |
| Palmitoyltransferase (EC 2.3.1.225) | ZDHHC20 | B4DRN8 | 1 |
| Palmitoyltransferase (EC 2.3.1.225) (Fragment) | ZDHHC1 | I3L202 | 1 |
| Palmitoyltransferase (EC 2.3.1.225) (Fragment) | ZDHHC5 | E9PMA5 | 1 |