\begin{columns}
\begin{column}{0.3\textwidth}
\end{column}
\begin{column}{0.7\textwidth}
\end{column}
\end{columns}
\usepackage{adjustbox}
\begin{adjustbox}{width=1.2\textwidth,center}
\end{adjustbox}
\begin{figure}
\advance\leftskip-2cm
\includegraphics[width=12cm]{result_struct_prot.pdf}
\end{figure}
\setbeamersize{text margin left=30mm,text margin right=30mm}
globally by the t class option:
\documentclass[t]{beamer}
for single frames with the same option locally:
\begin{frame}[t]
...
\end{frame}