Do you have your other private keys saved somewhere? Your master key? Or your active key? Your memo key?
Besides, you can't use your posting key to sign transfers anyway. The good thing is that you can install the Steem KeyChain browser extension from Google Play. It allows you to make transfers with only your Active Key.
$rewarding 25% 15 min
According to their post if you sign in the wallet with the master, it will allow you download a PDF of all your keys.
Those users who are inputting their Master Password for everything will now get a warning that informs them when they are attempting to sign in with the incorrect key or password, and gently guides them toward either getting the weakest key (the posting key) or downloading a PDF backup of all their keys.
https://steemit.com/steem/@steemitblog/social-condenser-is-live
Be sure not to lose it or expose it.
What you can do is install Steem KeyChain. It can generate all your other keys from your Master Key. I recommend not using it anywhere else.