The ubiquitin ligase SspH1 from Salmonella uses a modular and dynamic E3 domain to catalyze substrate ubiquitylation.

SspH/IpaH bacterial effector E3 ubiquitin (Ub) ligases, unrelated in sequence or structure to eukaryotic E3s, are utilized by a wide variety of Gram-negative bacteria during pathogenesis. These E3s function in a eukaryotic environment, utilize host cell E2 ubiquitin-conjugating enzymes of the Ube2D family, and target host proteins for ubiquitylation. Despite several crystal structures, details of Ube2D∼Ub binding and the mechanism of ubiquitin transfer are poorly understood. Here, we show that the catalytic E3 ligase domain of SspH1 can be divided into two subdomains: an N-terminal subdomain that harbors the active-site cysteine and a C-terminal subdomain containing the Ube2D∼Ub-binding site. SspH1 mutations designed to restrict subdomain motions show rapid formation of an E3∼Ub intermediate, but impaired Ub transfer to substrate. NMR experiments using paramagnetic spin labels reveal how SspH1 binds Ube2D∼Ub and targets the E2∼Ub active site. Unexpectedly, hydrogen/deuterium exchange MS shows that the E2∼Ub-binding region is dynamic but stabilized in the E3∼Ub intermediate. Our results support a model in which both subunits of an Ube2D∼Ub clamp onto a dynamic region of SspH1, promoting an E3 conformation poised for transthiolation. A conformational change is then required for Ub transfer from E3∼Ub to substrate.

The ubiquitin-conjugating enzyme, UbcM2, is restricted to monoubiquitylation by a two-fold mechanism that involves backside residues of E2 and Lys48 of ubiquitin.

Proteins can be modified on lysines (K) with a single ubiquitin (Ub) or with polymers of Ub (polyUb). These different configurations and their respective topologies are primary factors for determining whether substrates are targeted to the proteasome for degradation or directed to nonproteolytic outcomes. We report here on the intrinsic ubiquitylation properties of UbcM2 (UBE2E3/UbcH9), a conserved Ub-conjugating enzyme linked to cell proliferation, development, and the cellular antioxidant defense system. Using a fully recombinant ubiquitylation assay, we show that UbcM2 is severely limited in its ability to synthesize polyUb chains with wild-type Ub. Restriction to monoubiquitylation is governed by multiple residues on the backside of the enzyme, far removed from its active site, and by lysine 48 of Ub. UbcM2 with mutated backside residues can synthesize K63-linked polyUb chains and to a lesser extent K6- and K48-linked chains. Additionally, we identified a single residue on the backside of the enzyme that promotes monoubiquitylation. Together, these findings reveal that a combination of noncatalytic residues within the Ubc catalytic core domain of UbcM2 as well as a lysine(s) within Ub can relegate a Ub-conjugating enzyme to monoubiquitylate its cognate targets despite having the latent capacity to construct polyUb chains. The two-fold mechanism for restricting activity to monoubiquitylation provides added insurance that UbcM2 will not build polyUb chains on its substrates, even under conditions of high local Ub concentrations.

Nurses and subordination: a historical study of mental nurses' perceptions on administering aversion therapy for 'sexual deviations'.

This study aimed to examine the meanings that nurses attached to the 'treatments' administered to cure 'sexual deviation' (SD) in the UK, 1935-1974. In the UK, homosexuality was considered a classifiable mental illness that could be 'cured' until 1992. Nurses were involved in administering painful and distressing treatments. The study is based on oral history interviews with fifteen nurses who had administered treatments to cure individuals of their SD. The interviews were transcribed for historical interpretation. Some nurses believed that their role was to passively follow any orders they had been given. Other nurses limited their culpability concerning administering these treatments by adopting dehumanising and objectifying language and by focussing on administrative tasks, rather than the human beings in need of their care. Meanwhile, some nurses genuinely believed that they were acting beneficently by administering these distinctly unpleasant treatments. It is envisaged that this study might act to reiterate the need for nurses to ensure their interventions have a sound evidence base and that they constantly reflect on the moral and value base of their practice and the influence that science and societal norms can have on changing views of what is considered 'acceptable practice'.

'Queer' treatments: giving a voice to former patients who received treatments for their 'sexual deviations'.

AIMS AND OBJECTIVES: The study aimed to examine the experiences of patients and meanings attached to 'treatments' of sexual deviations, which included homosexuality and transvestism, in the UK (1949-1992), exploring reasons for such treatments, experiences and how individual lives were affected. BACKGROUND: Male homosexuality remained illegal in England until 1967 and, along with transvestism, was considered an antisocial sexual deviation that could be cured. Homosexuality remained classifiable as a mental illness until 1992. Nurses were involved in administering treatments to cure these individuals; however, there is a paucity of information about this now-discredited mental health nursing practice. DESIGN: A nationwide study based on oral history interviews. METHODS: Purposeful and snowball sampling was utilised when selecting participants for the study. Participants were recruited via adverts in gay establishments/media. All participants gave signed informed consent. Face-to-face oral history interviews were conducted and transcribed for historical interpretation. RESULTS: Seven former male patients made contact, aged 65-97 years at interview. All reported that the treatments had been unsuccessful in altering their sexual desires or behaviour. Most sought treatment owing to unsupportive and negative attitudes from friends, family and wider society. Others selected treatments instead of imprisonment. Most eventually found happiness in same-sex relationships. However, all were left feeling emotionally troubled by the treatments they received. CONCLUSION: Defining homosexuality and transvestism as mental illnesses and implementing what could be argued to be inefficient treatments to eradicate them appears to have had a lasting negative impact on the patients who received them. RELEVANCE TO CLINICAL PRACTICE: Nurses who care for older gay, lesbian, bisexual and transgender patients need to be mindful of their potential past treatment by healthcare services and ensure that they are non-judgmental and accepting of their sexual orientation and current gender.

'Gay times': identity, locality, memory, and the Brixton squats in 1970's London.

Through a thick description of a gay squatting community in south London in the 1970s, this piece explores the ways in which local histories complicate broader accounts of gay life, politics, and culture. Such a focus alerts us to the impact of personal encounters, of local politics, and material circumstances, of coincident local communities, of jobs (or the lack of them), and of major local events (like the Brixton riots of 1981). The local focus and the oral history sources also illuminate the complex ways in which unspoken and often unconscious imperatives associated with ethnicity, class, and the familial, social, and cultural contexts of our upbringings are played out under new and changing circumstances. Taking this approach fractures homogenizing assumptions about gay identity and community--even of a self-identified gay community like this squatting collective. It can also decentre sexuality as a primary category of identity and analysis as other factors come into sharper focus and shed light on the ebb and flow of identification and on the ways in which broader histories are woven into everyday lives. The piece thus considers different scales of analysis, the limits of identification, the inclusions and exclusions enacted when communities come together and identities coalesce, the continuities and discontinuities between broader and counter cultures (especially in relation to ideas and lived experiences of home), and the way memories of the squats and of the 1970s are modulated by subsequent national and gay politics, by AIDS, and by a profound sense of loss.