Date on Honors Thesis

Fall 12-5-2020

Major

Biology

Minor

Chemistry

Examining Committee Member

Dr. Christopher Lennon, Advisor

Examining Committee Member

Dr. Sterling Wright, Committee Member

Examining Committee Member

Dr. Ricky Cox, Committee Member

Abstract/Description

Inteins (intervening proteins) invade genes at the DNA level and splice out at the protein level. Once thought of as only a parasitic type of a mobile genetic element, recent work suggests a mutualistic relationship has formed in some cases within bacterial and archaeal hosts. After translation, a precursor protein is formed with the intein between two exteins. The intein is catalytic and can excise itself out through protein splicing. Intein insertion is biased towards the active site of the protein and is thought to cause inactivation of the host protein prior to splicing. Intein splicing is responsive to a number of environmental cues, suggesting that conditional protein splicing may serve as a novel form of post-translational regulation. The Pyrococcus horikoshii (Pho) RadA intein will splice in response to substrate single-stranded DNA (ssDNA). Splicing of this protein is inhibited when ssDNA is not present through intein-extein interactions. In this study, the Pho RadA intein was moved from its native position to alternative locations within the RadA sequence. In all alternative positions tested, the intein could no longer splice, even though predictive methods suggest it should. The results provide a greater understanding of intein site selection and point towards a rather complex evolutionary relationship between the intein and its hosts.

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