Public Keyring Security

[Mark]

With the posts of backing up files and anonymous private keys it got me
thinking. Is there a mechanism in place that protects (encrypts) a
public keyring? They can be thought of as sort of an address book or
contact list and with some mail providers encrypting contacts I wondered
if such a thing existed with pgp keys? 

Obviously I know you can install it an encrypted volume (depending on
your OS) but was curious if the program or even the "pgp standard" took
that into consideration or am I just too bored and that it's a stupid idea?