Initial Off-Cycle PE Email Response

Hi WSO, I am a second-year analyst at a boutique and have been receiving emails for one-off type of opportunities from headhunters. I initially heavily considered just staying for associate so I never really prepped for PE recruiting or any of the process.

I just received an email for a potential opportunity (lower MM) that I could be interested in. What is the etiquette for responding here? Do I attach a resume/do I need a longer email explaining my reasons for interest, etc.