Nascent-polypeptide-associated complex alpha polypeptide, also known as NACA, is a protein

Protein

Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...

 which in humans is encoded by the NACA gene

Gene

A gene is a molecular unit of heredity of a living organism. It is a name given to some stretches of DNA and RNA that code for a type of protein or for an RNA chain that has a function in the organism. Living beings depend on genes, as they specify all proteins and functional RNA chains...

.

Function

NACA prevents short recently synthesized (i.e., nascent) ribosome

Ribosome

A ribosome is a component of cells that assembles the twenty specific amino acid molecules to form the particular protein molecule determined by the nucleotide sequence of an RNA molecule....

-associated polypeptides from inappropriate interactions with cytosol

Cytosol

The cytosol or intracellular fluid is the liquid found inside cells, that is separated into compartments by membranes. For example, the mitochondrial matrix separates the mitochondrion into compartments....

ic proteins. NACA binds nascent-polypeptide domains emerging from ribosomes unless it contains a signal peptide

Signal peptide

A signal peptide is a short peptide chain that directs the transport of a protein.Signal peptides may also be called targeting signals, signal sequences, transit peptides, or localization signals....

 which is fully exposed. Depletion of NACA from ribosomes carrying nascent polypeptides allows the signal recognition particle

Signal recognition particle

The signal recognition particle is an abundant, cytosolic, universally conserved ribonucleoprotein that recognizes and targets specific proteins to the endoplasmic reticulum in eukaryotes and the plasma membrane in prokaryotes....

 (SRP) to crosslink to polypeptides regardless of whether or not they contain signal peptides or not. In the absence of NACA, proteins lacking signal peptides can be mis-translocated into the endoplasmic reticulum

Endoplasmic reticulum

The endoplasmic reticulum is an organelle of cells in eukaryotic organisms that forms an interconnected network of tubules, vesicles, and cisternae...

.

The NACA protein is expressed in bone during development

Developmental biology

Developmental biology is the study of the process by which organisms grow and develop. Modern developmental biology studies the genetic control of cell growth, differentiation and "morphogenesis", which is the process that gives rise to tissues, organs and anatomy.- Related fields of study...

 and acts as a transcriptional coactivator

Coactivator (genetics)

A coactivator is a protein that increases gene expression by binding to an activator which contains a DNA binding domain. The coactivator is unable to bind DNA by itself....

 in conjunction with acidic activators.

Interactions

NACA has been shown to interact

Protein-protein interaction

Protein–protein interactions occur when two or more proteins bind together, often to carry out their biological function. Many of the most important molecular processes in the cell such as DNA replication are carried out by large molecular machines that are built from a large number of protein...

 with BTF3

BTF3

Transcription factor BTF3 is a protein that in humans is encoded by the BTF3 gene.-Further reading:...

, FADD

FADD

Fas-Associated protein with Death Domain is an adaptor molecule that bridges the Fas-receptor, and other death receptors, to caspase-8 through its death domain to form the death-inducing signaling complex during apoptosis. -Signalling:...

, C-jun

C-jun

c-Jun is the name of a gene and protein that, in combination with c-Fos, forms the AP-1 early response transcription factor. It was first identified as the Fos-binding protein p39 and only later rediscovered as the product of the c-jun gene. It is activated through double phosphorylation by the...

, and 3 members of taxilin

TXLNA

Alpha-taxilin is a protein that in humans is encoded by the TXLNA gene.-Further reading:...

family.

Further reading