Kyra Sedgwick’s never lived with one character as long as she’s lived with Brenda Leigh Johnson, the endearingly driven cop at the center of TNT’s “The Closer.”

And as the pair enter their fifth season together on Monday, with Brenda newly married to Fritz (Jon Tenney), the actress, who’s been married to Kevin Bacon since 1988 but who once worried she’d eventually be bored playing Brenda, finds she’s anything but.

“Surprisingly, it’s been exciting and wonderful and really nice to get deeper into a character,” Sedgwick, 43, said in a phone interview last month.

“I think aging with a character and growing with a character, and seeing a character through life changes and, you know, relationship changes is actually a really fascinating thing to do,” she said.

“But I must say that on my hiatuses, I really do like to do something else. And I have been able to,” thanks to “The Closer’s” six-month shooting schedule and 15-episode seasons.

Sedgwick plays a role behind the scenes as well. This year, she’s an executive producer, a role she describes as more about “consulting” than anything else.

“You know, honestly, it’s always been a really collaborative group. I’ve been really lucky that way, everybody’s been very inclusive from the get-go. It’s just now that I can be maybe a little bit more vocal about some things that I might have sort of been vocal about, but a little more tiptoeing around,” she said.

“I can’t get involved in casting on a week-to-week basis, because that’s something that I would never have time to do,” she said.

Casting for this season includes a multi-episode appearance by the “wonderful” Mary McDonnell (“Battlestar Galactica”), Sedgwick said.

“She comes in as an internal affairs officer who’s my opposite in every way, and we’re sort of antagonists, and I think it’s nice, and different, for Brenda to have a female antagonist,” she said.

“This year’s about change, and you know change is not something that Brenda deals with very well. Obviously, the most obvious change is that she’s married, and how do you go through life as a married person, rather than a single person? There’s change in the squad. Provenza (G.W. Bailey) has a girlfriend, so that’s new and different,” she said.