33kDa

33 kDa refers to a molecular weight of roughly 33,000 daltons, and is used to describe a protein or polypeptide whose mass is near 33 kilodaltons. It is not a single, universal protein; many different proteins across species have masses in this range, so the term is a descriptor of size rather than a unique identity.

Mass estimates are typically obtained by SDS-PAGE with molecular-weight standards, or by more precise methods such as mass spectrometry or size-exclusion chromatography. The apparent mass in a gel or analytical technique is an approximation and can be influenced by factors such as amino acid composition, overall charge, post-translational modifications, metal or ligand binding, or association with other molecules. In native conditions, proteins may form dimers or higher-order assemblies, which can alter their observed mass compared to the monomer.

A rough rule of thumb is that a 33 kDa protein consists of about 300 amino acids, assuming an average residue mass of ~110 Da. Actual length varies with sequence composition and processing; proteins that oligomerize may have subunits with masses far from 33 kDa, while complexes can complicate direct mass interpretation.

In scientific literature, the term 33 kDa is commonly used as a descriptive label for proteins, bands, or subunits around that mass. There is no universal gene or protein defined by the name; instead, many distinct proteins in different organisms may be described as "33 kDa" in various studies. Context such as species, gene name, or experimental details is required to identify the specific protein referred to.