CAPE ELIZABETH, Maine (AP) _ Robert R. Masterton, chairman, president and chief executive officer of The One Bancorp, has died from an inoperable brain tumor. He was 58.

Masterton, who had been in grave condition since December, died at his southern Maine home late Sunday, Roy P. Hibyan, president of the company's Maine Savings Bank subsidiary, said Monday.

Masterton joined Maine Savings Bank in 1967, and rose to the offices of chairman and chief executive The One Bancorp in September 1987.

During his time with the company, its assets grew to $2 billion from $150 million, partly due to interstate acquisitions.

Masterton helped draw up the 1975 Maine interstate banking laws, considered the most advanced of any state at the time they were enacted. The banking laws allowed interstate banking on a reciprocal basis with banks in other states.

Frederick W. Pape Jr. was elected May 9 to succeed Masterton as acting head of The One Bancorp and Maine Savings Bank. A search for a chief operating officer is continuing.

Robert Raynor Masterton was born in Boston on April 26, 1930.

He received his undergraduate degree in economics from Northeastern University in 1953 and his master's degree in business administration from the Harvard Graudate School of Business Administration in 1957.

Masterton was survived by his wife of 35 years, Nancy; a son, Peter, of Windham, a daughter, Laurie Tuchman of Scarsdale, N.Y.; his mother, of Pocasset, Mass., and three granchildren.

Funeral arrangements were pending.