Protein / target

Small ribosomal subunit protein bS21

rpsUP68679Escherichia coli (strain K12)Swiss-Prot
UniProt: P68679NCBI Gene: 947577
30
Clinical trials
8
Drugs targeting

Protein at a glance

Biological role

Structural constituent of ribosome

Derived from structured UniProt, Open Targets and literature data on this page.

Protein profile

UniProt 2026_02

Canonical identity and biological annotation from UniProt.

Function

Probably involved in recognition of ribosome rescue factor SmrB in stalled/collided disomes; fusion of protein fragments to its N-terminus decreases ribosome rescue in the presence of SmrB (PubMed:35264790)

Domains and Gene Ontology detail (7)

Gene Ontology

  • Ccytoplasm
  • Ccytosol
  • Ccytosolic small ribosomal subunit
  • FrRNA binding
  • Fstructural constituent of ribosome
  • Pcytoplasmic translation
  • Pribosomal small subunit assembly

71 aa · 9 kDa

Drugs targeting this protein

8

Whether each drug engages this protein directly or through a complex, and how many other targets are recorded for it. Direct binders with few recorded targets are listed first.

Azithromycin
Inhibitor

Bacterial 70S ribosome inhibitor

Acts on a complex — shared with rpsL, rpsR, rpsD +51 more · 1 of 55 recorded protein targets — broad pharmacology

Doxycycline
Inhibitor

Bacterial 70S ribosome inhibitor

Acts on a complex — shared with rpsL, rpsR, rpsD +51 more · 1 of 59 recorded protein targets — broad pharmacology

Neomycin
Inhibitor

Bacterial 70S ribosome inhibitor

Acts on a complex — shared with rpsL, rpsR, rpsD +51 more · 1 of 55 recorded protein targets — broad pharmacology

Clarithromycin
Inhibitor

Bacterial 70S ribosome inhibitor

Acts on a complex — shared with rpsL, rpsR, rpsD +51 more · 1 of 55 recorded protein targets — broad pharmacology

Erythromycin
Inhibitor

Bacterial 70S ribosome inhibitor

Acts on a complex — shared with rpsL, rpsR, rpsD +51 more · 1 of 55 recorded protein targets — broad pharmacology

Sisomicin
Inhibitor

Bacterial 70S ribosome inhibitor

Acts on a complex — shared with rpsL, rpsR, rpsD +51 more · 1 of 55 recorded protein targets — broad pharmacology

eravacycline
Inhibitor

Bacterial 70S ribosome inhibitor

Acts on a complex — shared with rpsL, rpsR, rpsD +51 more · 1 of 55 recorded protein targets — broad pharmacology

Tetracycline
Inhibitor

Bacterial 70S ribosome inhibitor

Acts on a complex — shared with rpsL, rpsR, rpsD +51 more · 1 of 55 recorded protein targets — broad pharmacology

ChEMBL mechanism, action type and target identity. Open Targets clinical status and indications.

Clinical trials

30

Trials of drugs that target this protein — reached indirectly through those drugs, so a trial listed here studies the drug, not the protein.

Pre-delivery Administration of Azithromycin to Prevent Neonatal Sepsis and Death: a Phase III Double-blind Randomized Clinical TrialPHASE3

COMPLETED · via Azithromycin · NCT03199547

Randomized Clinical Trial: Use of Azithromycin to Prevent Lung Damage in Preterm Newborns Under Mechanical VentilationPHASE4

COMPLETED · via Azithromycin · NCT03485703

Autologous Stem Cell Transplant With Pomalidomide (CC-4047®) Maintenance Versus Continuous Clarithromycin/ Pomalidomide / Dexamethasone Salvage Therapy in Relapsed or Refractory Multiple Myeloma: A Phase 2 Open-Label Randomized Study by Tristate ConsortiumPHASE2

COMPLETED · via Clarithromycin · NCT01745588

Effect of WHO-yaws Elimination Strategy in Lihir Island, Papua New GuineaPHASE3

COMPLETED · via Azithromycin · NCT01955252

Role of Add-on Azithromycin in the Management of Patients With Acute Exacerbation of Idiopathic Pulmonary FibrosisNA

RECRUITING · via Azithromycin · NCT05842681

Daily Doxy: Study of Persons Receiving Daily Doxycycline to Inform Sexually Transmitted Infection Prophylaxis RegimensPHASE4

COMPLETED · via Doxycycline · NCT06545656

Show remaining trials (24)
Efficacy of Adding Azithromycin to Cephalosporin for the Prophylaxis Against Infectious Morbidity Following Cesarean Delivery in High Risk WomenPHASE4

COMPLETED · via Azithromycin · NCT04062175

A Study of Intranasal Live Attenuated Influenza Vaccine Immunogenicity and Associations With the Nasopharyngeal Microbiome Among Children in the Gambia - The NASIMMUNE StudyPHASE4

COMPLETED · via Azithromycin · NCT02972957

Parallel Group, Double Blinded, 1:1, Randomized Controlled Phase III Trial of Co-trimoxazole Versus Azithromycin for the Treatment of Undifferentiated Fever In NepalPHASE3

COMPLETED · via Azithromycin · NCT02773407

The Value of Antibiotic Treatment of Exacerbations of Hospitalised COPD PatientsPHASE4

COMPLETED · via Doxycycline · NCT00170222

Phase II Clinical Trial of Doxycycline 50 mg or 100 mg Daily for the Prevention of Skin Toxicity in Patients With Metastatic Colorectal Cancer Treated With Anti-EGFR and ChemotherapyPHASE2

COMPLETED · via Doxycycline · NCT03448731

Preterm Premature Rupture of Membranes: Erythromycin Versus Azithromycin a Randomized Trial Comparing Their Efficacy to Prolong Latency (PEACE Trial)PHASE3

WITHDRAWN · via Azithromycin · NCT01556334

Azithromycin and Cefixime Combination Versus Azithromycin Alone for the Out-patient Treatment of Clinically Suspected or Confirmed Uncomplicated Typhoid Fever in South Asia; a Randomised Controlled TrialPHASE4

COMPLETED · via Azithromycin · NCT04349826

A Phase III Double-blind, Randomised, Placebo Controlled Trial of Long Term Therapy on Exacerbation Rate in Patients With Stable COPD Using DoxycyclinePHASE3

COMPLETED · via Doxycycline · NCT02305940

Efficacy and Safety of Azithromycin Compared to the Base Therapeutic Regiment of Hydroxychloroquine in Moderate to Severe COVID-19: A Randomized, Controlled, Double-Blind, Clinical TrialPHASE4

UNKNOWN · via Azithromycin · NCT04359316

Repurposing Clinically Approved Drugs for Yaws With an Insight Into the Cutaneous Ulcer Disease Syndrome (Trep-AByaws)PHASE3

COMPLETED · via Azithromycin · NCT05764876

Treatment Failure and Associated Predictors Following Azithromycin Treatment for Urogenital Chlamydial Infection in Males in Youth Correctional FacilitiesPHASE2

COMPLETED · via Azithromycin · NCT03249935

Nutritional Support for Lactating Women and Azithromycin to Infants to Improve Growth Outcomes in Peri-urban Slums of Karachi, Pakistan - Randomized Controlled TrialNA

COMPLETED · via Azithromycin · NCT03564652

An Open-Label Pilot Study of Fundamental Modification of the Gut Microbiota in the Treatment of Refractory Crohn's DiseasePHASE2

COMPLETED · via Neomycin · NCT03476317

The Effect of Clarithromycin on Mortality and Morbidity in Patients With Ischemic Heart Disease - a Randomized, Placebo Controlled, Double Blinded, Multicentre, Clinical TrialPHASE3

COMPLETED · via Clarithromycin · NCT00121550

Azithromycine Pour la Vie Des Enfants au Niger - Implémentation et Recherche: Essai mortalité et résistance (Azithromycin for Child Survival in Niger: Mortality Trial and Resistance Trial)PHASE4

COMPLETED · via Azithromycin · NCT04224987

Antenatal Azithromycin to Prevent Preterm Birth in Pregnant Women With Vaginal Cerclage. A Randomized Controlled TrialPHASE4

COMPLETED · via Azithromycin · NCT04278937

Randomised Evaluation of COVID-19 TherapyPHASE3

RECRUITING · via Azithromycin · NCT04381936

LAKANA , a Cluster-randomized, Double-blinded, Parallel Group, Controlled Trial, Testing the Effects of Mass Drug Administration of Azithromycin on Mortality and Other Outcomes Among 1-11 Month Old Infants in Rural Mali.PHASE3

COMPLETED · via Azithromycin · NCT04424511

Relationship Between Gastric Emptying and Glycemic Variability in Type 1 Diabetes MellitusPHASE1

COMPLETED · via Erythromycin · NCT02755064

A Drug-Drug Interaction Study of Zanubrutinib With Moderate and Strong CYP3A Inhibitors in Patients With B-Cell MalignanciesPHASE1

COMPLETED · via Clarithromycin · NCT04551963

Intra-articular Doxycycline: A Novel Treatment of Adhesive CapsulitisPHASE4

COMPLETED · via Doxycycline · NCT03479502

Open Study of Clarithromycin for the Treatment of Infections Caused by Nontuberculous Mycobacteria (NTM)PHASE4

COMPLETED · via Clarithromycin · NCT00600769

Doxycycline Host-directed Therapy to Improve Lung Function and Decrease Tissue Destruction in Pulmonary Tuberculosis: A Phase III Randomized Control Trial (Doxy-TB)PHASE3

RECRUITING · via Doxycycline · NCT05473520

A Single Arm, Open-label Exploratory Clinical Trial of Azithromycin in Pulmonary SarcoidosisPHASE2

COMPLETED · via Azithromycin · NCT04020380

ClinicalTrials.gov via the drug-target graph.

What's happening now

31

Recent activity around this target, drawn from one canonical event stream. Every item is reached through 8 drugs that target this protein, so each event is news about that drug rather than about the protein directly.

  1. Industry development2026-07-23
    Fe-doped BiVO4/g-C3N4 heterojunction for efficient tetracycline degradation under low-intensity UV irradiation

    Nature — Environmental Sciences · news · via Tetracycline

  2. Label change2026-06-12

    Label change: DOXYCYCLINE (ANDA204234)

    fda · regulatory · fda · via Doxycycline

  3. Label change2025-04-25

    Label change: DOXYCYCLINE (ANDA204234)

    fda · regulatory · fda · via Doxycycline

  4. Label change2025-04-25

    Label change: DOXYCYCLINE (ANDA204234)

    fda · regulatory · fda · via Doxycycline

  5. Label change2025-03-31

    Label change: DOXYCYCLINE (ANDA207757)

    fda · regulatory · fda · via Doxycycline

  6. New publication2024-09-27
    Impact of pneumococcal conjugate vaccines on invasive pneumococcal disease-causing lineages among South African children.

    Nature communications · 2024 · 13 citations · Europe PMC · via Erythromycin

  7. New publication2024-01-30
    Guidelines of care for the management of acne vulgaris.

    Journal of the American Academy of Dermatology · 2024 · 236 citations · Europe PMC · via Doxycycline

  8. New publication2021-05-02
    New Antibiotics for Multidrug-Resistant Bacterial Strains: Latest Research Developments and Future Perspectives.

    Molecules (Basel, Switzerland) · 2021 · 302 citations · Europe PMC · via Sisomicin

  9. Safety communication2020-12-17

    Drug Safety Update: Erythromycin: update on known risk of infantile hypertrophic pyloric stenosis

    mhra · safety · mhra · via Erythromycin

  10. Safety communication2020-12-17

    Drug Safety Update: Erythromycin: caution required due to cardiac risks (QT interval prolongation); drug interaction with rivaroxaban

    mhra · safety · mhra · via Erythromycin

  11. New publication2020-09-01
    Risk of QT Interval Prolongation Associated With Use of Hydroxychloroquine With or Without Concomitant Azithromycin Among Hospitalized Patients Testing Positive for Coronavirus Disease 2019 (COVID-19).

    JAMA cardiology · 2020 · 465 citations · Europe PMC · via Azithromycin

  12. Label change2020-07-08

    Label change: DOXYCYCLINE (ANDA207757)

    fda · regulatory · fda · via Doxycycline

Objective event titles are shown unmodified; the event kind and significance line are derived from structured fields. Forefront AttentionEvent stream aggregating Europe PMC Regulatory filings ClinicalTrials.gov.