Functional study of the Saccharomyces cerevisiae Nha1p C-terminus

Area of Science:

• Cellular biology
• Molecular biology
• Biochemistry

Background:

• Saccharomyces cerevisiae possesses an alkali metal cation antiporter, Nha1p, encoded by the NHA1 gene.
• Nha1p exhibits broad substrate specificity (Na+, Li+, K+) and a unique long C-terminus.

Purpose of the Study:

• To investigate the role of the C-terminus in Nha1p function.
• To determine the necessity of the C-terminus for plasma membrane localization and substrate transport.

Main Methods:

• Construction and expression of 13 truncated NHA1 versions in an S. cerevisiae strain.
• Analysis of antiporter localization, substrate specificity, and cellular tolerance to alkali metal cations.

Main Results:

• The entire C-terminus is not essential for plasma membrane localization or transport of Na+, Li+, K+, and Rb+.
• Partial C-terminal truncation (approx. 70 amino acids) enhances cellular tolerance to Na+, Li+, and Rb+.
• Specific C-terminal regions (amino acids 883-928) are crucial for maximal Nha1p activity towards Na+ and Li+.
• The C-terminus plays a role in regulating intracellular K+ content and responding to osmotic stress.

Conclusions:

• The C-terminus of Nha1p is not essential for its basic function but modulates its activity and cellular responses.
• Specific domains within the C-terminus are critical for optimal antiporter function and cellular adaptation to ionic and osmotic challenges.