- RAB, member RAS oncogene (RAB)

- Receptor accessory proteins (REEP)
- Receptor (G protein-coupled) activity modifying proteins (RAMP)
- Receptor transporter proteins (RTP)
- Regulators of G-protein signaling (RGS)

- Relaxin family peptide receptors (RXFP)
- RetNet (Retinal Information Network)
- Rho GTPase activating proteins (ARHGAP)
- Rho guanine nucleotide exchange factors (ARHGEF)
- Ribonucleases, RNase A (RNASE)
- S ribosomal proteins (RPS)
- RPG Ribosomal Protein Gene Database
- L ribosomal proteins (RPL)
- RPG Ribosomal Protein Gene Database
- RING-type zinc fingers (RNF)
- SAM and SH3 domain containing (SASH)
- Sodium channels (SCN)

- Secretoglobins (SCGB)

- Secreted frizzled-related proteins (SFRP)
- Semaphorins (SEMA)

- Serine peptidases (PRSS)
- Serine (or cysteine) peptidase inhibitors (SERPIN)

- Serine peptidase inhibitors, Kazal type (SPINK)
- Shisa homologs (SHISA)
- Short chain dehydrogenase/reductase superfamily (SDR)
- Sialic acid binding Ig-like lectins(SIGLEC)
- Sideroflexins (SFXN)
- Signal-regulatory proteins (SIRP)
- SKI transcriptional corepressors (SKOR)
- SMADs (SMAD)
- Small G protein signaling modulators (SGSM)
- Snail homologs (SNAI)
- Solute carriers (SLC)
- Sorting nexins (SNX)
- Specificity protein/Kruppel-like transcription factors
- Speedy homologs (SPDY)
- SRY (sex determining region Y)-boxes (SOX)

- StAR-related lipid transfer (START) domain containing (STARD)
- Structural maintenance of chromosomes proteins (SMC)
- Sulfotransferases, cytosolic (SULT)
- Sulfotransferases, membrane-bound
- Suppressors of cytokine signaling (SOCS)
- Taste receptors (TAS#R)
- T-boxes (TBX)

- T cell receptors (TR)
- Teashirt zinc fingers (TSHZ)
- Tectonic proteins (TCTN)
- THO complex (THOC)
- Trace amine associated receptors (TAAR)
- Trafficking protein particle complex (TRAPPC)
- Transglutaminases (TGM)
- Transmembrane and coiled-coil domain containing (TMCC)
- Trinucleotide (CAG) repeat containing (TNRC)
- Tripartite motif containing (TRIM)

- Tropomyosins (TPM)
- Tubulins (TUB)
- Tumor necrosis factor (ligand) superfamily (TNFSF)

- Tumor necrosis factor receptor superfamily (TNFRSF)
