An apparatus includes an elongated member configured for transoral placement into a stomach, and a distal end effector including first and second members configured to engage stomach tissue, e.g., tissue beyond the esophageal junction. The first and second members are movable relatively toward one another generally in a first plane, and the distal end effector is movable relative to the elongated member in a second plane generally transverse to the first plane. A third member of the distal end effector is configured to engage stomach tissue. The third member is movable in a distal direction relative to the first and second members. A tissue securement member of the apparatus is coupled to at least one of the first and second members for securing together tissue engaged thereby. The tissue securement member includes first and second parts, a suture attached to the first part, and a securing element attached to the suture and configured for engagement with the second part when the first and second members move relatively toward one another to engage tissue, to thereby secure the second part to the first part.