Essay --

This paper aims to describe the role and function of protein Helicase. "Helicases are enzymes that use ATP-driven motor force to unwind double-stranded DNA or RNA" (Wu, 2012). First discovered in E Coli in 1976 (Abdel-Monem et al, 1976) with the first eukaryotic helicase protein discovered soon after in 1978 (Hotta & Stern, 1978). Since these discoveries, many more similar enzymes and proteins have been discovered. It breaks the hydrogen bonds formed between opposing strands of DNA with energy formed through the hydrolysis of ATP to ADP and inorganic phosphate (Hartsuiker, 2013). The separation of strands is necessary as newly formed strands need to be transcribed using the nucleotide sequence of an open DNA strand. The protein is built around 6 sub-units which form an hexameric ring with assymetic symmetry. The biochemical properties of helicases are all very similar however, the presence of specific motifs (short chains of DNA, primarily used for structure) alters which family of helicases they fall into, how that specific helicase will work and subsequently; mutations in these specific motifs will cause specific differences in protein synthesis. There are 4 'Superfamilies' created through differentiation of 7 conserved motifs, roughly made from 300-500 amino acids(Hall & Matson, 2002). All helicases covered in this paper belong the largest family(Unmate et al, 2011) Super Family 2 (SF2) which are recognized by 9 conserved motifs. XPB and XPD are both DNA helicase structures, mutations in their helicase motifs can cause Xeroderma Pigmentosum (XP) and similar diseases. XPD and XPD's cellular functions involve Nucleotide Excision Repair, which removes DNA; damaged from UV rays. During Xeroderma Pigmentosum, these damaged stran... ..., similar to BLM, XPD, XPB, and WRN is found in Super family 2 and is a part of the DEAH box helicases. These helicases are involved in nuclear transcription and control of gene expression (De La Cruz et al, 1999). Mutations to this gene coding protein can result in an individual suffering from ATR-X syndrome, causing psychomotor retardation, ÃŽ ±-thalassemia and the expression of abnormal phenotypes in both the genitals and face. A 2kb deletion mutation has been observed in the XH2 gene, removing both coding and non-coding sequences. This mutation results in the down-regulation of ÃŽ ± - globin, this irregular haemoglobins are produced which directly results in ÃŽ ± - thalassemia (Gibbons et al, 1995). The mutated globin proteins have a lower affinity with oxygen, thus less oxygen is in the blood, and less oxygen reaches the brain which can trigger psychomotor retardation.