module: dmel_larval_serum_protein_hexamers
title: Larval serum protein hexamerins in Drosophila melanogaster
label: Larval serum protein hexamers
module_type: PROTEIN_COMPLEX
description: >-
  Larval serum proteins (LSPs) are hexamerins, storage proteins related to
  arthropod hemocyanins that have lost the copper-binding oxygen-carrying
  function. They are made in large amounts by the larval fat body, secreted into
  the hemolymph, and taken back up by the fat body at the end of the third
  instar, where they are stored in granules and broken down to supply amino
  acids for metamorphosis. Lsp1 hexamers are made of the alpha, beta and gamma
  chains (Lsp1alpha, Lsp1beta, Lsp1gamma) in various combinations, and Lsp2 forms
  a separate hexamer.
summary: >-
  Fat-body-made hexamerin storage proteins (Lsp1 and Lsp2 hexamers) that supply
  amino acids for metamorphosis.
concepts:
  - {id: GO:0140089, label: protein storage}
cellular_components:
  - {id: GO:0005576, label: extracellular region}
parts:
  - id: lsp1_hexamer
    label: Lsp1 hexamer
    role: Lsp1 alpha, beta and gamma hexamer
    group: LSP1
    complex_label: Lsp1 hexamer
    function: {id: GO:0045735, label: nutrient reservoir activity}
  - id: lsp2_hexamer
    label: Lsp2 hexamer
    role: Lsp2 homohexamer
    complex: false
    genes: [Lsp2]
    function: {id: GO:0045735, label: nutrient reservoir activity}
notes: >-
  No GO cellular component term specifically describes a hexamerin complex, so
  the module is grounded to the protein storage process instead; the parts are labelled as Lsp1 and Lsp2
  hexamers. Lsp2 forms homohexamers and is modelled as a single-gene part.
  Lsp1 hexamers mix the three Lsp1 chains in several combinations; the exact
  subunit stoichiometries are not modelled. Receptor-mediated uptake of LSPs by
  the fat body at the end of larval life is outside the module. Lsp2 is also
  expressed in the adult fat body.