Dear mohammad pooya Naghshbandi ,

It depends (of course) on which one you mean but according to:

https://www.mybiosource.com/nrtn-active-protein/neurturin-protein-nrtn/969414

The corresponding PDB file is can be found here:

https://www.uniprot.org/uniprot/Q99748

Scroll down and you find secondary structure, you can also use FASTA form and perform a secondary structure prediction using:

https://npsa-prabi.ibcp.fr/cgi-bin/npsa_automat.pl?page=/NPSA/npsa_sopma.htmltructure

or

http://helios.princeton.edu/CONCORD/

Hope this answers your question.