In molecular biology, the cyclin-dependent kinase regulatory subunit family is a family of

proteins Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, re ...

consisting of the regulatory subunits of cyclin-dependent protein kinases. In eukaryotes, cyclin-dependent protein kinases

interact Advocates for Informed Choice, dba interACT or interACT Advocates for Intersex Youth, is a 501(c)(3) nonprofit organization advocating for the legal and human rights of children with intersex traits. The organization was founded in 2006 and fo ...

with

cyclins Cyclins are proteins that control the progression of a cell through the cell cycle by activating cyclin-dependent kinases (CDK). Etymology Cyclins were originally discovered by R. Timothy Hunt in 1982 while studying the cell cycle of sea urch ...

to regulate

cell cycle The cell cycle, or cell-division cycle, is the sequential series of events that take place in a cell (biology), cell that causes it to divide into two daughter cells. These events include the growth of the cell, duplication of its DNA (DNA re ...

progression, and are required for the G1 and G2 stages of

cell division Cell division is the process by which a parent cell (biology), cell divides into two daughter cells. Cell division usually occurs as part of a larger cell cycle in which the cell grows and replicates its chromosome(s) before dividing. In eukar ...

. The proteins

bind BIND () is a suite of software for interacting with the Domain Name System (DNS). Its most prominent component, named (pronounced ''name-dee'': , short for ''name Daemon (computing), daemon''), performs both of the main DNS server roles, acting ...

to a regulatory subunit, cyclin-dependent kinase regulatory subunit (CKS), which is essential for their function. This regulatory subunit is a small protein of 79 to 150 residues. In

yeast Yeasts are eukaryotic, single-celled microorganisms classified as members of the fungus kingdom (biology), kingdom. The first yeast originated hundreds of millions of years ago, and at least 1,500 species are currently recognized. They are est ...

(gene CKS1) and in

fission yeast ''Schizosaccharomyces pombe'', also called "fission yeast", is a species of yeast used in traditional brewing and as a model organism in molecular and cell biology. It is a unicellular eukaryote, whose cells are rod-shaped. Cells typically measu ...

(gene suc1) a single

isoform A protein isoform, or "protein variant", is a member of a set of highly similar proteins that originate from a single gene and are the result of genetic differences. While many perform the same or similar biological roles, some isoforms have uniqu ...

is known, while

mammal A mammal () is a vertebrate animal of the Class (biology), class Mammalia (). Mammals are characterised by the presence of milk-producing mammary glands for feeding their young, a broad neocortex region of the brain, fur or hair, and three ...

s have two highly related

isoforms A protein isoform, or "protein variant", is a member of a set of highly similar proteins that originate from a single gene and are the result of genetic differences. While many perform the same or similar biological roles, some isoforms have uniqu ...

. The regulatory subunits exist as hexamers, formed by the

symmetrical Symmetry () in everyday life refers to a sense of harmonious and beautiful proportion and balance. In mathematics, the term has a more precise definition and is usually used to refer to an object that is invariant under some transformations ...

assembly of 3 interlocked homodimers, creating an unusual 12-stranded

beta-barrel In protein structures, a beta barrel (β barrel) is a beta sheet (β sheet) composed of tandem repeats that twists and coils to form a closed toroidal structure in which the first strand is bonded to the last strand (hydrogen bond). Beta-strands ...

structure. Through the barrel centre runs a 12A diameter tunnel, lined by 6 exposed

helix A helix (; ) is a shape like a cylindrical coil spring or the thread of a machine screw. It is a type of smooth space curve with tangent lines at a constant angle to a fixed axis. Helices are important in biology, as the DNA molecule is for ...

pairs. Six kinase units can be modelled to bind the hexameric structure, which may thus act as a hub for cyclin-dependent protein kinase multimerisation. This family includes the

CKS1B Cyclin-dependent kinases regulatory subunit 1 is a protein that in humans is encoded by the ''CKS1B'' gene. Function The CKS1B protein binds to the catalytic subunit of the cyclin-dependent kinases and is essential for their biological functio ...

and CKS2 genes in mammals.

References

External links

* {{ELM, DOC_CKS1_1 Cell cycle regulators Protein domains