Spätzle or spaetzle (

German German(s) may refer to: * Germany, the country of the Germans and German things **Germania (Roman era) * Germans, citizens of Germany, people of German ancestry, or native speakers of the German language ** For citizenship in Germany, see also Ge ...

for a type of noodle) is an evolutionarily-conserved

arthropod Arthropods ( ) are invertebrates in the phylum Arthropoda. They possess an arthropod exoskeleton, exoskeleton with a cuticle made of chitin, often Mineralization (biology), mineralised with calcium carbonate, a body with differentiated (Metam ...

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 ...

first identified in ''

Drosophila melanogaster ''Drosophila melanogaster'' is a species of fly (an insect of the Order (biology), order Diptera) in the family Drosophilidae. The species is often referred to as the fruit fly or lesser fruit fly, or less commonly the "vinegar fly", "pomace fly" ...

''. It plays a role in

embryonic development In developmental biology, animal embryonic development, also known as animal embryogenesis, is the developmental stage of an animal embryo. Embryonic development starts with the fertilization of an egg cell (ovum) by a sperm, sperm cell (spermat ...

and in the insect

innate immune response The innate immune system or nonspecific immune system is one of the two main immunity strategies in vertebrates (the other being the adaptive immune system). The innate immune system is an alternate defense strategy and is the dominant immune s ...

. The name was coined by the Nobel laureate

Christiane Nüsslein-Volhard Christiane (Janni) Nüsslein-Volhard (; born 20 October 1942) is a German developmental biologist and a 1995 Nobel Prize in Physiology or Medicine laureate. She is the only woman from Germany to have received a Nobel Prize in the sciences. N� ...

after the

Spätzle Spätzle (), Spätzla or Spatzen, called ''nokedli'' () in Hungarian, are a type of Central European egg pasta typically served as a side for meat dishes with sauce. Commonly associated with Swabia (hence Swabian spaetzle) and Alsace, it is als ...

noodle-like form of homozygous mutant fly larvae.

Structure

Spätzle has a

cystine knot A cystine knot is a protein structural motif containing three disulfide bridges (formed from pairs of cysteine residues). The sections of polypeptide that occur between two of them form a loop through which a third disulfide bond passes, form ...

structure supported by

disulfide bridge In chemistry, a disulfide (or disulphide in British English) is a compound containing a functional group or the anion. The linkage is also called an SS-bond or sometimes a disulfide bridge and usually derived from two thiol groups. In inorg ...

s, is

glycosylated Glycosylation is the reaction in which a carbohydrate (or ' glycan'), i.e. a glycosyl donor, is attached to a hydroxyl or other functional group of another molecule (a glycosyl acceptor) in order to form a glycoconjugate. In biology (but not ...

, and naturally forms a

homodimer In biochemistry, a protein dimer is a macromolecular complex or protein multimer, multimer formed by two protein monomers, or single proteins, which are usually Non-covalent interaction, non-covalently bound. Many macromolecules, such as proteins ...

. Multiple forms are produced by

alternative splicing Alternative splicing, alternative RNA splicing, or differential splicing, is an alternative RNA splicing, splicing process during gene expression that allows a single gene to produce different splice variants. For example, some exons of a gene ma ...

. It is produced as a preprotein, and needs to be activated by a

serine protease Serine proteases (or serine endopeptidases) are enzymes that cleave peptide bonds in proteins. Serine serves as the nucleophilic amino acid at the (enzyme's) active site. They are found ubiquitously in both eukaryotes and prokaryotes. Serin ...

called . The signal sequence spz -25is first cleaved, followed by the spz 6-220fragment, leaving the final spz 21-326(Spaetzle C-106) part as the mature protein.

Function

Homodimeric ''spz'' binds to a dimeric toll receptor in fruit flies and related organisms, thus activating the signaling cascade.

Embryonic development

A ligand of the ''toll'' pathway, ''spz'' is involved in the formation of the dorso-ventral axis in embryonic development.

References

{{reflist __notoc__ Drosophila melanogaster genes