I am trying to create an nr database, from the nr files provided by NCBI, on a server to run some blast searches. Once I try to run the blast search, the following error is returned

blastp -query ngruberi_TTL1.fasta -db /home/sh17a/nr
BLAST Database error: No alias or index file found for protein database [/home/sh17a/nr] in search path [/home/sh17a::]

The nr directory contains the files from decompressing nr.112.tar.gz from ftp://ftp.ncbi.nlm.nih.gov/blast/db/, which yields the following:

nr.112.phd nr.112.phr nr.112.pnd nr.112.pog nr.112.ppi nr.112.psi taxdb.btd nr.112.phi nr.112.pin nr.112.pni nr.112.ppd nr.112.psd nr.112.psq nr.pal taxdb.bti

However, referencing the directory that contains all of these files as the database for the blast search does not seem to work and spits out the error above.

Is there any way to fix this? Or, is there any other way of making the nr database so that I can reference it as a single root file?

Thanks