module: dmel_nascent_polypeptide_associated_complex
title: Nascent polypeptide-associated complex in Drosophila melanogaster
label: Nascent polypeptide-associated complex
module_type: PROTEIN_COMPLEX
description: >-
  The nascent polypeptide-associated complex (NAC) is a heterodimer of an alpha
  and a beta subunit that binds near the exit tunnel of translating ribosomes and
  contacts emerging nascent chains. It acts as a ribosome-associated chaperone
  and sorting factor that shields nascent polypeptides and regulates their
  access to the signal recognition particle and to other targeting pathways.
  Drosophila has two alpha-subunit genes (Nacalpha and gNacalpha) and an
  expanded family of beta-subunit (BTF3-like) genes: bicaudal (bic), uncNacbeta
  and a cluster of betaNACtes genes, the latter expressed in the male germline.
summary: >-
  Ribosome-associated alpha/beta heterodimer that binds emerging nascent chains,
  with paralogous alpha and beta subunits.
concepts:
  - {id: GO:0005854, label: nascent polypeptide-associated complex}
parts:
  - id: nac_alpha
    label: NAC alpha subunit
    role: alpha subunit of the NAC heterodimer
    variant_sets:
      - id: nac_alpha_variants
        label: Alpha subunit paralogs
        selection: ONE_OR_MORE
        variants:
          - {id: nacalpha, label: Nacalpha, genes: [Nacalpha]}
          - {id: gnacalpha, label: gNacalpha, genes: [gNacalpha]}
  - id: nac_beta
    label: NAC beta subunit
    role: beta subunit of the NAC heterodimer
    variant_sets:
      - id: nac_beta_variants
        label: Beta subunit paralogs
        selection: ONE_OR_MORE
        variants:
          - {id: bic, label: bicaudal (bic), genes: [bic]}
          - {id: uncnacbeta, label: uncNacbeta, genes: [uncNacbeta]}
          - id: betanactes
            label: betaNACtes paralogs
            genes: [betaNACtes1, betaNACtes2, betaNACtes3, betaNACtes4, betaNACtes6]
            complex: false
notes: >-
  Parts follow FlyBase subgroups NACA and NACB. Which alpha and beta paralogs
  pair in vivo, and in which tissues, is not resolved for most combinations;
  the variants record the paralogs available for each subunit position. The
  betaNACtes genes are grouped as one variant because they are near-identical
  testis-expressed copies.
function_note: >-
  No molecular function is assigned: NAC binds ribosomes at the exit tunnel
  and emerging nascent chains, and its subunits carry only ribosome binding
  terms in GOA.