Functional analysis of conserved hypothetical proteins from the Antarctic yeast, Glaciozyma antarctica PI12

Abstract

Aims: Recent discoveries have revealed that Glaciozyma antarctica PI12 has been discovered to encode numerous protein-coding genes that are crucial for thermal adaptation. However, more than 35% of the protein-coding genes for this species were identified as hypothetical proteins (HP). Nevertheless, over 35% of the protein-coding genes for this species were classified as hypothetical proteins (HP). Previous studies have documented the role of these uncharacterized proteins in the physiological regulation and cold adaptation of psychrophilic microorganisms. Thus, we aim to identify the structural features of the conserved HPs that were ideal for their function in response to temperature stress. Methodology and results: Three conserved HPs of G. antarctica, designated GaHP2, GaHP3 and GaHP4, were cloned, expressed purified and their function and structure were evaluated. Functional analysis showed that these proteins maintained their activities at low temperatures below 25 °C, but at a lower reaction rate. Meanwhile, thermal unfolding assays revealed the stability of GaHP2 and GaHP4 at high temperatures (43 °C), suggesting their non-ATPbinding chaperone activity. The comparative structural analysis demonstrated that the HPs exhibited cold-adapted traits, most notably increased flexibility in their 3D structures. For GaHP2, the aromatic residues can be linked to its heat stability. GaHP4's cold shock domain implies it regulates gene transcription and translation during temperature fluctuations. Conclusion, significance and impact of study:This study has established the structure-function relationships of the G. antarctica HPs and provided fundamental experimental data highlighting their importance in thermal stress response by maintaining a balance between molecular stability and structural flexibility.