IT Security covers wide range of domains such as Network Security, Server Security, Application Security, Storage Security, Database Security.
Information Security is portmanteau of multiple domains with Continuous Business Operations, Business Strategy and as well as Information Technology.
IT Security is only Defensive in Nature such as Anti-Virus, Firewalls, Intrusion Detection/Prevention Systems, Anti-Malware.
Information Security is always proactive in nature. It is a superset of Information Technology. InfoSec is usually offensive in nature!
IT is a business support function and not a top-down approach. Information Technology is mainly driven by strategic Information Security Leaders at the top-level.
Information Security is Proactive and Offensive as well as provides strategic leadership to Information Technology. It covers the entire organisational security that goes farther than Information Technology.