All articles starting with P

Protein (nutrient)

Protein (nutrient): dietary macronutrient of amino acid chains needed for cell repair and growth; essential amino acids must come from food; US guidance moved from 0.8 to 1.2–1.6 g/kg/day in 2026.

Protein AC81, encoded by baculovirus gene ac81 (ORF81, AcMNPV), is a 233-aa core viral protein and putative disulfide isomerase working with P33; required for budded virus production, ODV envelopment, and occlusion body embedding.

Protein argonaute-4

Protein argonaute-4 (AGO4) is an Argonaute-family small-RNA effector: in Arabidopsis it directs RNA-directed DNA methylation via 24-nt siRNAs, while in mammals it is a catalytically inactive paralog with roles in male meiosis and antiviral defense.

Protein BANP

Protein BANP (BTG3-associated nuclear protein, SMAR1, UniProt Q8N9N5) is a BEN-domain transcription factor binding unmethylated CGCG motifs at CpG island promoters, methylation-sensitive, chromatin-opening, tumor-suppressive; unrelated to BPN protein powder supplements.

Protein beta

Protein beta is a conserved bacterial protein family, best characterized in bacteriophage P4, whose beta protein stops the phage's gop product from killing E. coli.

Protein Binding

Protein binding: noncovalent, high-specificity association of a protein with a ligand, quantified by Kd (millimolar to femtomolar). Studied by ITC, SPR, fluorescence; plasma protein binding governs drug free fraction.

Oct 22, 2026

Protein bioconjugation

Protein bioconjugation is the creation of a covalent link between a protein and another molecule, and underlies approved therapeutics including antibody-drug conjugates and PEGylated proteins such as Neulasta.

Protein biosynthesis

Protein biosynthesis, also called peptide biosynthesis, is the process by which cells build proteins: ribosomes translate messenger RNA into amino acid chains, producing up to 150,000 human proteins.

Protein C

Protein C is a vitamin K-dependent plasma zymogen activated by thrombin-thrombomodulin to APC, which with protein S inactivates factors Va and VIIIa; deficiency causes thrombophilia and neonatal purpura fulminans, treatable with CEPROTIN concentrate.

Oct 22, 2026

Protein cage

A protein cage is a hollow, shell-like nanostructure of self-assembled protein subunits, a few to tens of nanometers wide, seen in viral capsids and ferritin.

Protein CBFA2T3

CBFA2T3 (MTG16, ETO2, RUNX1T3, ZMYND4) is a human transcriptional corepressor of the MTG family, key in hematopoietic stem cell fate and targeted by t(16;21) and CBFA2T3::GLIS2 leukemia fusions.

Protein Cms1

Protein Cms1 (IPR032704) is a conserved eukaryotic protein family spanning fungal and plant Cms1 and metazoan CMSS1, a putative 90S preribosome subunit with a P-loop NTPase/DEAD-box helicase-like domain; yeast Cms1p overexpression suppresses an mcm10 mutant.

Protein contact dermatitis

Protein contact dermatitis (PCD), first described by Hjorth and Roed-Petersen in 1976, is a chronic IgE-mediated eczema from immediate protein hypersensitivity, mainly occupational in food handlers, with negative patch tests and positive prick tests.

Protein crystallization

Protein crystallization is the laboratory method of growing ordered crystals of purified proteins, driven by supersaturation, so their structures can be solved by X-ray crystallography.

Protein crystallography

Protein crystallography is a structural biology method that determines a protein's three-dimensional atomic structure from X-ray diffraction patterns of protein crystals, producing atomic coordinates deposited in the Protein Data Bank.

Protein Data Bank

The Protein Data Bank (PDB) is the open-access archive of experimentally determined 3D structures of proteins and other biological macromolecules, established in 1971 at Brookhaven National Laboratory.

Protein deficiency

Protein deficiency: inadequate dietary protein causing impaired growth, immunity, and albumin synthesis; ICD-11 code 5B71. Severe form in children is kwashiorkor (edema, fatty liver), contrasted with marasmus; 42.8 million under-5s wasted in 2024.

Protein deficiency anaemia

Protein deficiency anaemia, also called amino-acid deficiency anaemia, is ICD-11 code 3A03.1: anaemia from low body protein, usually normocytic, seen in protein-energy undernutrition, kwashiorkor, and tropical pregnancy-associated disease.

Protein dimer

Protein dimer: a complex of two protein monomers, homodimer (identical chains) or heterodimer (different chains); common quaternary structure regulating enzyme activation, signaling, and allostery, exemplified by hemoglobin's αβ dimers.

Protein Disulfide Isomerase

Protein disulfide isomerase (PDI, EC 5.3.4.1), an endoplasmic reticulum enzyme discovered by Anfinsen in 1963, catalyzes disulfide bond formation, reduction, and isomerization during protein folding and, when secreted, regulates thrombosis and cancer progression.

Protein disulfide-isomerase SCO2

SCO2 (synthesis of cytochrome c oxidase 2) is a thioredoxin-fold mitochondrial inner-membrane protein with a CX3C copper site that acts as a copper-dependent thiol reductase in COX2 CuA maturation; biallelic mutations cause fatal infantile cardioencephalomyopathy.

Protein Domains

Protein domains: independently folding, functional structural units of proteins, classified by SCOP, CATH, and Pfam; a few thousand folds build millions of proteins, now classified at scale by TED across AlphaFold.

Protein down-regulated in DIF1 11

Protein down-regulated in DIF1 11 (InterPro IPR040220) is a plant protein family, DUF784-related with a prolamin-like domain, named for genes downregulated in Arabidopsis dif1 ovules lacking embryo sacs.

Protein DPCD

Protein DPCD (deleted in primary ciliary dyskinesia homolog; HGNC 24542, UniProt Q9BVM2) is a 203-amino-acid ciliary protein linked to ciliogenesis, R2TP/Akt signaling, and PCD candidate status, distinct from the FDA's Division of Patient-Centered Development.

Protein EARLY FLOWERING 4 domain

EARLY FLOWERING 4 domain (Pfam PF07011, DUF1313), a plant-specific alpha-helical homodimer domain in ELF4 circadian clock proteins of the Evening Complex, unrelated to the animal ETS transcription factor ELF4.

Protein electrophoresis

Protein electrophoresis is a laboratory method separating proteins in a gel under an electric field; SDS-PAGE estimates molecular weight, and clinical serum electrophoresis detects monoclonal proteins.

Protein engineering

Protein engineering creates proteins with enhanced or novel functions via rational design, directed evolution, and AI-driven computational design; recognized by the 1993, 2018, and 2024 Chemistry Nobel Prizes and applied in therapeutics, agriculture, and industrial enzymes.

Protein EXORDIUM-like

Protein EXORDIUM-like (EXO/EXL, PHI-1 family) are small apoplastic plant proteins regulating cell expansion downstream of brassinosteroid signaling; Arabidopsis EXO was found by promoter trapping in 2003, and the eight-member family also mediates carbon and salt responses.

Protein farnesyltransferase subunit beta

Protein farnesyltransferase subunit beta (FNTB, chromosome 14q23.3) is the catalytic, zinc-binding subunit of farnesyltransferase (EC 2.5.1.58), the heterodimeric enzyme that farnesylates Ras and other CAAX proteins and is the target of FTIs such as lonafarnib, approved for progeria in 2020.