VEVEY, Switzerland — Dmitri Nabokov, the only child of acclaimed novelist Vladimir Nabokov who helped protect and translate his father's work while also pursuing careers as an opera singer and race car driver, has died. He was 77.

The younger Nabokov died Wednesday at a hospital in Vevey after a long illness, literary agent Andrew Wylie said Friday. He had been hospitalized in January with a lung infection.

Dmitri Nabokov spent much of his life trying to carve a life away from the shadow of his father, whose books "Lolita" and "Pale Fire" are regarded as some of the best English prose ever written.

The Harvard-educated son was a mountain climber, opera singer, race car driver and playboy. But Dmitri Nabokov always returned to protecting his father's legacy, translating and editing his father's plays, poems, stories, the novella "The Enchanter" and "Selected Letters."

"My father is gradually marching — with his two favorite writers, Pushkin and Joyce — arm in arm into the pantheon to join the greatest of all, Shakespeare, who is waiting for them," Nabokov said in a 2009 interview. "I like to think that I did my bit to keep things on track." After the success of "Lolita," Dmitri Nabokov translated his father's "Invitation to a Beheading" from Russian, and after his father's death, he wrote the memoir "On Revisiting Father's Room."

In 1962, the younger Nabokov began to race cars competitively and until 1982 he maintained an active professional operatic career as a basso profundo.

After the death of his mother in 1991, he sold the remainder of the Nabokov archive to the New York Public Library and attended conferences dedicated to his father.

Vladimir Nabokov had to borrow to send his son to Harvard in 1951. He said Dmitri's interests there were "mountaineering, girls, music, track, tennis and his studies, in that order. … He is completely and as it were dazzlingly fearless, loved by his friends, endowed with a magnificent brain, but a stranger to study."

In 2009, the author's son decided controversially to publish his father's final, fragmentary novel "The Original of Laura," which was written on index cards in 1975-77, the last years of his life. It was an act he said went against his father's wishes, who had asked that it be burned.

Dmitri Nabokov's early life was nomadic. Vladimir Nabokov and his family fled the chaos of the Russian Civil War and moved to Paris, but they had to flee again in 1940, this time from the Nazis. He took his Jewish wife, Vera, and then 6-year-old Dmitri, their only child, to the United States. Vladimir Nabokov became an American citizen in 1945 but returned to Europe in 1961 after the great success of "Lolita," settling in Switzerland.

Dmitri Nabokov never married, but believed that he would have made a great father, as his own was.

"He was a father like any other loving father. He didn't sacrifice games with his son for his work. He never forgot about his family. He taught me various sports. He taught me to read and write, in the best sense of the terms. I think I was one of the few children who had formal grammar lessons. He shared everything," he said.