Johnson, who pinch-hit in the eighth for second baseman Diory Hernandez and remained in the game, drove a 1-1 pitch a couple of rows behind the short fence in the right-field corner for his eighth home run after a one-out walk to Adam LaRoche.
It was the fifth homer allowed this season by Mota, making his second appearance since last Tuesday's well-documented dust-up with Milwaukee slugger Prince Fielder.
Rookie Kris Medlen (3-3) pitched two hitless innings for the win, striking out four and walking one. The right-hander struck out Andre Ethier, Manny Ramirez and Matt Kemp in the eighth after a leadoff walk to Rafael Furcal. In 16 relief appearances this season, Medlen has 29 strikeouts in 27 2-3 innings.
Rafael Soriano, who served up Ethier's three-run walkoff homer in Thursday's series opener, got three outs for his 17th save in 19 attempts despite giving up an RBI double to Ethier in the 10th.
The right-hander retired Kemp on a on a grounder to shortstop Yunel Escobar, who robbed him of a tying RBI single with a diving play toward the middle and threw him out after an intentional walk to Ramirez.
Dodgers left-hander Clayton Kershaw and Braves 34-year-old rookie Kenshin Kawakami matched zeros through seven innings in a matchup of pitchers facing their respective opponents for the first time. Kershaw threw 104 pitches, allowing two hits and striking out 10. Kawakami made 125 pitches, scattering four singles and striking out four.
Kershaw struck out 10 of his first 18 batters, retiring 20 of 22 after Ryan Church opened the game with a double into the left field corner. Atlanta's only other hit against the 21-year-old right-hander was a one-out single in the fourth by Garret Anderson. The only walk Kershaw allowed was to Escobar, whom he picked off to end the seventh.
Braves third baseman Chipper Jones missed his second straight game because of a strained oblique muscle on his left side, which occurred while he took batting practice on Friday. The Braves are 10-9 this season in games that he doesn't start.
NOTES: Because of the Dodgers' 12-inning loss on Friday night and the Yankees' 15-inning win over Boston, Los Angeles entered Saturday not having the best record in the majors for the first time since May 2, when the team was 16-8. ... Ross' error was his first in 29 starts this season behind the plate. ... Kershaw is 6-1 with a 1.06 ERA in his last 10 starts beginning with a no-decision on June 16 - the best ERA in the majors during that stretch. ... Braves RHP Tim Hudson's next scheduled rehab start is next Thursday with Triple-A Gwinnett, which will be preceded by a bullpen session on Monday. He is working his way back from Tommy John surgery.