Kinesin-associated protein 3 (KAP3) is a

protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residue (biochemistry), residues. Proteins perform a vast array of functions within organisms, including Enzyme catalysis, catalysing metab ...

that in humans is encoded by the ''KIFAP3''

gene In biology, the word gene has two meanings. The Mendelian gene is a basic unit of heredity. The molecular gene is a sequence of nucleotides in DNA that is transcribed to produce a functional RNA. There are two types of molecular genes: protei ...

. It is a non-motor, accessory subunit which co-oligomerizes with the motor subunits KIF3A and

KIF3B Kinesin-like protein KIF3B is a protein that in humans is encoded by the ''KIF3B'' gene. KIF3B is an N-type protein that complexes with two other kinesin proteins to form two-headed anterograde motors. First, KIF3B forms a heterodimer with KIF3A ...

or KIF3C, to form heterotrimeric kinesin-2 motor proteins. Kinesin-2 KAP subunits were initially characterized in echinoderms and mice.

Function

The small G protein GDP dissociation stimulator ( smg GDS) is a regulator protein having two activities on a group of small G proteins including the

Rho Rho (; uppercase Ρ, lowercase ρ or ; or ) is the seventeenth letter of the Greek alphabet. In the system of Greek numerals it has a value of 100. It is derived from Phoenician alphabet, Phoenician letter resh . Its uppercase form uses the same ...

and

Rap1 Rap1 (Ras-proximate-1 or Ras-related protein 1) is a small GTPase, which are small cytosolic proteins that act like cellular switches and are vital for effective signal transduction. There are two isoforms of the Rap1 protein, each encoded by ...

family members and Ki-Ras; one is to stimulate their GDP/GTP exchange reactions, and the other is to inhibit their interactions with membranes. The protein encoded by this gene contains 9

Armadillo repeats An armadillo repeat is a characteristic, repetitive amino acid peptide sequence, sequence of about 42 residue (chemistry)#biochemistry, residues in length that is found in many proteins. Proteins that contain armadillo repeats typically contain sev ...

and interacts with the smg GDS protein through these repeats. This protein, which is highly concentrated around the

endoplasmic reticulum The endoplasmic reticulum (ER) is a part of a transportation system of the eukaryote, eukaryotic cell, and has many other important functions such as protein folding. The word endoplasmic means "within the cytoplasm", and reticulum is Latin for ...

, is

phosphorylated In biochemistry, phosphorylation is described as the "transfer of a phosphate group" from a donor to an acceptor. A common phosphorylating agent (phosphate donor) is ATP and a common family of acceptor are alcohols: : This equation can be writt ...

v-src v-Src is a gene found in Rous sarcoma virus (RSV) that encodes a tyrosine kinase that causes a type of cancer in chickens. The src gene is oncogenic as it triggers uncontrolled growth in abnormal host cells. It was the first retroviral oncogen ...

, and this phosphorylation reduces the affinity of the protein for smg GDS. It is thought that this protein serves as a linker between human chromosome-associated polypeptide ( HCAP) and KIF3A/B, a

kinesin A kinesin is a protein complex belonging to a class of motor proteins found in eukaryotic cells. Kinesins move along microtubule (MT) filaments and are powered by the hydrolysis of adenosine triphosphate (ATP) (thus kinesins are ATPases, a typ ...

superfamily protein in the nucleus, and that it plays a role in the interaction of chromosomes with an ATPase motor protein. It has also been proposed to act as a clamp, stabilizing the C-terminal half of the otherwise unstable stalk coiled-coil.

Interactions

KIFAP3 has been shown to interact with APC,

SMC3 Structural maintenance of chromosomes protein 3 (SMC3) is a protein that in humans is encoded by the SMC3 gene. SMC3 is a subunit of the Cohesin complex which mediates sister chromatid cohesion, homologous recombination and DNA looping. Cohesin ...

and RAP1GDS1.

Function

Interactions

References

Further reading