Beta-crystallin B1 is a
protein that in humans is encoded by the ''CRYBB1''
gene.
Variants in CRYBB1 are associated with autosomal dominant
congenital cataract.
Crystallins
In anatomy, a crystallin is a water-soluble structural protein found in the lens and the cornea of the eye accounting for the transparency of the structure. It has also been identified in other places such as the heart, and in aggressive breast c ...
are separated into two classes:
taxon-specific, or enzyme, and ubiquitous. The latter class constitutes the major proteins of vertebrate
eye lens and maintains the transparency and refractive index of the lens. Since lens central fiber cells lose their
nuclei during development, these crystallins are made and then retained throughout life, making them extremely stable proteins.
Mammalian lens crystallins are divided into alpha, beta, and gamma families; beta and gamma crystallins are also considered as a superfamily. Alpha and beta families are further divided into
acidic and basic groups. Seven protein regions exist in crystallins: four
homologous
Homology may refer to:
Sciences
Biology
*Homology (biology), any characteristic of biological organisms that is derived from a common ancestor
*Sequence homology, biological homology between DNA, RNA, or protein sequences
* Homologous chrom ...
motifs, a connecting
peptide, and N- and C-terminal extensions.
Beta-crystallins, the most heterogeneous, differ by the presence of the C-terminal extension (present in the basic group, none in the acidic group). Beta-crystallins form aggregates of different sizes and are able to self-associate to form dimers or to form
heterodimers
In biochemistry, a protein dimer is a macromolecular complex formed by two protein monomers, or single proteins, which are usually non-covalently bound. Many macromolecules, such as proteins or nucleic acids, form dimers. The word ''dimer'' ha ...
with other beta-crystallins. This gene, a beta basic group member, undergoes extensive cleavage at its
N-terminal
The N-terminus (also known as the amino-terminus, NH2-terminus, N-terminal end or amine-terminus) is the start of a protein or polypeptide, referring to the free amine group (-NH2) located at the end of a polypeptide. Within a peptide, the ami ...
extension during lens maturation. It is also a member of a gene cluster with
beta-A4,
beta-B2, and
beta-B3.
References
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